If you play a seven of any color, you may, at your option, swap your hand with any other player (probably the person with the fewest cards).
Blocking: If the person you chose to swap with has a seven of any color, they may play it to block the swap.
Upping the Ante: If the erstwhile swapper got blocked and is holding another seven, he may play it to force the trade. The next player can then block again, and the swapper can up the ante again, etc. The last person to play a 7 decides the outcome.
Stealing the win: If one person is holding a seven as his last card (i.e. he has "uno") and another player plays a seven to swap with him, if the "uno" guy blocks and the swapper has another seven, he gives his hand to the guy with no cards, thereby giving him all his points, and steals the win for himself.
Top card may be changed: Over the course of the blocking and ante-upping, the top card may be changed from the original. The next player to play must play off of the new top card, not the original.
On calling "Uno" No one may call "uno" on one of the swapping players until the transaction has been completed. This caveat needed to be added as an unscrupulous player discovered he could increase the number of cards he was passing.
If a zero of any color is played, all players must pass their hand to the person on their right, or their left, depending on the direction of play (i.e. the direction has been changed with a 'Reverse' card).
Ettiquite: It is considered good form for the person who just played a zero to indicate who should go next. This is because all the hand passing is rather disorienting and it's easy to lose track of who's turn it is.
Giving Your Nieghbor the Win: If you have only one card and that card is a zero, playing it on your turn will immediately give the person next to you the win (say, the person to your left), and you'll be stuck with whatever cards the person before you had (say, the person to your right). In this way, holding a zero as your last card is kind of like holding the Old Maid.
Point to Ponder: Matching not possible / unlikely: While there are two copies of any given color-card in a standard deck (e.g. two green 6s, two blue 'Draw Two's), there is only one copy of each zero. That means you can never match a zero. The only time this is not the case is when your group is playing with more than one deck (we usually play with two). Even then, matching is tricky.
If someone plays a card and you have a card that matches it exactly (both the color and the number (or word)) you may play that card out of turn.
No Game Effects: The normal effects of the card (such as skip, draw two, etc.) have no effect if it is played as a match.
Going Out: It is possible to "go out" by matching.
Statute of Limitations: If you don't get in your match quick enough (possibly because the next player played to fast) you can still play your match as long as the card you're matching is no more than 1 card below the top card (not counting matches to the top card). Also, you must have said "match" or "oo-oo" or something similar to indicate that it was always your intention to match. Unanounced retroative matching is not legal.
Point to Ponder: It is possible to get rid of as many as 3 cards on your turn: (1) match the card of the player before you, (2) play a card, (3) match your own.
You can match 6s with 9s or 9s with 6s, as long as they are all of the same color. (This grew out of our inability to properly read whether it was a 6 or a 9 when matching.)
Top card may be changed: With this addendum, it is possible for the top card to be changed in the event of a match. The next player to go in the normal course of play will play off of the new top card, not the original.
Point to Ponder: With the "69" rule in effect, it is possible to get rid of as many as 7 cards on your turn. A possible scenario: (1) match a red 6 of the player before you, (2) match it again with two red 9s, (3) play a green 9 on top of the red one you just matched, (4) match your own green 9 with another, (5) match it again with two green 6s.
If half of the table (round down if there's an odd number) participates in a 6/9 matching (including the person who started it) everyone at the table may play, out of turn, as many cards of the same color as the 6s and 9s.
Minimum # of matchers: Regardless of the number of people at the table, the minimum number of matchers is 3. In other words, the person that played the first 6 or 9 (one) and two more matchers (plus two makes three). Otherwise, at a table of 5 people, you'd only need 1 matcher, which is a little low.
New Top Card: Whatever card ends up on top is the card the next person plays off of; it has no game effects, just like the starting card.
Going Out: It is possible to "go out" in a Color Crazy match if your whole hand consists of a single color.
With 'Draw Two' cards: If a 'Draw Two' is played on someone, rather than draw two, he can play another 'Draw Two' of any color and the player after him must draw four. The next player after him can play another 'Draw Two', which raises the count (aka "the stack") to six cards, and so on. The "stacking" ends when one player doesn't have a 'Draw Two'; then they get to draw however many cards are on the stack.
With 'Wild Draw Four' cards: Pretty much the same as with 'Draw Two' cards, except it increases by multiples of 4 instead.
No "Mix-n-Match": You can only stack 'Draw Two's on 'Draw Two's and you can only stack 'Wild Draw Four's on other 'Wild Draw Four's.
(Note: The following addendums arose from our realization that the most fun part of this UNO variant is the stacking rule and we wanted to "keep the fever going". It basically expands the stacking to include all the word cards.)
If you have a 'Draw Two' played on you, you can send it back to the person who just played it on you by playing a 'Reverse' that is the same color as the 'Draw Two' they played. The count of the stack does not increase, merely reverses.
Re-Reversing: The player that the stack was reversed onto can then play a 'Reverse' of any color to send it back to the previos reverser, and so on.
Continuing the stacking: Alternatively, the player the drawing was reversed onto can play another 'Draw Two' on the 'Reverse' that was just played to continue the stacking in the other direction. In this special circumstance, the 'Draw Two' does not have to match the color of the 'Reverse' that was just played. (In this way, D2s have the same semantics as WD4s.)
Reversing a 'Wild Draw Four': Pretty much the same as with the 'Draw Two's, except the color of the 'Reverse' must be of the color named by the person who just played the 'Wild Draw Four' on you. As per the "no mix and match" rule, 'Draw Two's are never part of a WD4 stack.
If you have a 'Draw Two' played on you, you can play a 'Skip' of the same color and have the drawing skip you and proceed to the next player after you.
(Aside: This is the only occasion where the meaning of a word card changes. When a 'Skip' is played in a stacking progression, you are not skipping the next person, but yourself instead.)
Lengthening the Delay of the Blast: The person after the skipper can likewise play a 'Skip' of any color to have it skip himself and onto the next person, and so on.
Reversing and Skipping: Per Addendum #1 above, at any time in the stacking, a player can play a 'Reverse' of the same color as the 'Skip' or 'Draw Two' just played to send it back to the previous player. Likewise, a 'Skip' played on a 'Reverse' must be the same color (as per normal Uno rules.)
Continuing the stacking: At any time, someone can play a 'Draw Two' to continue the stacking. As mentioned before, the 'Draw Two' does not need to be the same color as the 'Reverse' or 'Skip' just played. (As mentioned earlier, this gives D2s the same semantics as WD4s.)
Skipping with 'Wild Draw Four's: Pretty much the same as for the 'Draw Two's, except the color of the 'Skip' must be of the color named by the person who played the 'Wild Draw Four' on you. Again, 'Draw Two's are never part of a WD4 stack.
On any stacking progression ('Draw Two' or 'Wild Draw 4'), a person can play a 'Wild' card (a normal Wild, not a 'Wild Draw 4') and it "spreads" the drawing to every other person at the table.
Blocking: The only way to block a spreader is to play a 'Wild' of your own, either a normal 'Wild' or a 'Wild Draw 4', then you won't have to draw. You do not have to discard the 'Wild' or 'Wild Draw 4' after you block with it.
Turning it back on the spreader: If half of the people at the table (round down if there's an odd number of people) ends up playing a 'Wild', including the spreader (i.e. at a table of 8 or 9 people, 1 person spreads with a 'Wild' and 3 other people block with either a 'Wild' or a WD4, making 4 people en todo), the initial spreader must draw double the amount of the cards that were on the stack, and nobody else has to draw any. There is no way for the initial spreader to turn it back after that; it's done.
Minimum # of blockers: Regardless of the number of people at the table, the minimum number of blockers is 2 (making three 'Wild' players total). Otherwise, at a table of 5 people, only 1 blocker would be needed (which is a little low).
Ettiquite: People who are blocking should hold their 'Wild's up in front of them so everyone can count the number of blockers before they discard their 'Wild's. The spreader should play his 'Wild' on the table so he doesn't forget to discard it.
Picking the new color: The spreader picks the new color, regardless of how many people did or didn't block or whether it got turned back on him or not.
When a person plays a 'Draw Two' or 'Wild Draw 4' (possibly on a stacking progression) and it's his last card, that player is not out yet. One of the following things can happen.
Condition #s 1 - 3 don't come up very often, but it's always fun when they do.
The following are somewhat official, but we have modified them just a titch.
The dealer can deal any number of cards to each player. A reasonable range is within 5 to 15 starting cards.
Ettiquite: The scorekeeper doesn't have to shuffle or deal if he doesn't want to. (Scorekeeping is a big job.) Someone else can oblige with a "courtesy" shuffle / deal (usually just the next person in the rotation).
The starting card that is turned over cannot have the word "Wild" on it. (No 'Wild's or WD4s.) Keep turning over cards from the draw pile until you get a non-Wild.
The normal effects of the starting card do not apply. (The starting player is not skipped, doesn't need to draw two, etc.)
The player to the left of the dealer starts the round.
If you have no cards in your hand that you can play, you must draw until you get one you can play. This means you might end up drawing a whole bunch of cards.
If you have a card that you could play, but you don't want to play it (often occurs if you have only 1 card and it's a zero) you must show that card to everyone else, then draw one card, then it's the next person's turn.
Note: This differs slightly from the official rules. Officially, you don't have to show the card you could've played, just the honor system is used. We considered that a little squirrely and dispensed with the "honor" part.
Goofing up is penalized by drawing two cards. Some examples of penalties include:
At the end of each round, after someone has "gone out", scores for each hand should be tallied by adding together the values of each remaining card in your hand. Cards are worth the following:
Having a lower score is better (as in Hearts or Golf).
Scores are totaled up at the end of each round. At the end of N number of rounds (however many you decide to play) the person with the lowest total score wins.
People who arrive late: It's perfectly acceptable for someone to jump into the game late. They do not, however, start with a score of zero. Instead, inpterpolate a score for them by taking the average of the highest and lowest score. (Add the highest & lowest score together and divide the result by 2.)
People who leave early: If you leave the game before playing the last round, no score is recorded for you. (This is only important if you care about seeing your name on the chart.)
Point to Ponder: It is possible for more than one person to finish with a score of zero: the person that went out, and anyone else who is holding nothing but zeroes (one or more) in their hand. Alternatively, in a "color crazy" match, 2 (or more) people might have a hand that consists of a single color and they could both go out.