Should a character's motivation not be clearly enough fleshed-out by disadvantages, a character may take a motivation as a Quirk. Without a motivation, players will ask themselves why they embark on every adventure and gamemasters won't know how to tailor the adventure to a character's desires. .Here are some examples. Many of these are already covered by disadvantages.
Association - Character is a side-kick, relative, or friend of another character. Chewbacca
Goal - Character has a specific goal he wants to fulfill. Inigo Montoya wanted to kill the six-fingered man. The Goal could also be something like achieve a political office, gain magic powers, etc.
Glory - Character seeks personal renown, honor, and fame. Boromir
Greed - Character wants money. Very simple Motivation but also very shallow. Han Solo in Star Wars, Vazinni from Princess Bride.
Knowledge - Character wants to accrue knowledge. Goes well with a young character or someone with a high knowledge skill. Luke, Indiana Jones.
Political-Revolutionary/Patriot - Two options, characters are either for a nation (or other institution) or against one. Perhaps both. A mild form of Fanaticism.
Psychopath - Character is just plain crazy and gets in fights easily.
Redemption - Character wants to repent for previous sins. Xena, Angel
Responsibility - The character feels a responsibility or duty towards someone or something. Robin Hood and the Merry Men felt the responsibility to help the poor. A mild Sense of Duty.
Teacher/Mentor - Character feels the need to share with others his knowledge. This goes well with an elderly character. Fits well with a younger character whose Motive is Knowledge. Obi-Wan Kenobi, Mr. Miyagi.
Thrillseeker - Character adventures because it is fun.
Upholding the Good - The character is simply a good person who wants to help people. Hercules the Legendary Journeys, Superman, etc. This is probably the easiest.
Unwanted Involvement - The character does not want to be involved but somehow got caught up in adventuring. Willow, Bilbo
Vengeance - Character adventures as a way of exacting vengeance on bad guys. Batman.
Wanderer - Character wanderers around meeting people, having adventures, like Kane from Kung Fu. Characters motives may be shrouded in mystery.
Some classic adventure styles that are particularly well suited to the above motivations.