Q - Quina Quen
Easily the weirdest character in any FF game, Quina is a Qu. A race of androgynous chefs who are obsessed with food and little else. Quina has the ability to eat foes when they are weak and he sometimes gains new powers as a result. He uses giant cutlery as weapons and is generally quite odd. Quina is an optional party member and as such, doesn't feature strongly in the narrative. Still, he/she has a unique and interesting story arc......even if it is based on food.
R - Random Battles
Some people love random battle encounters and for some people it is the bane of their existence. They have largely been done away with now, with FF12 and 13 opting for enemies that can be seen from afar, though they've made somewhat for a comeback in FF13-2. Yes they can be frustrating when you are trying to get from A to B or you are in an early area so the battles are mega easy and give no reward, but for me Final Fantasy isn't quite right without random battles.
S - Sephiroth
The ultimate FF villain, Sephiroth was the result of injecting a human foetus with alien DNA. Yes, the result was long silver hair and an aptitude for wielding incredibly long swords. Driven mad by the discovery of his alien heritage, Sephiroth seeks the destruction of the world by bringing a huge comet down from space. Sephiroth has since featured in almost all FF7 related media, including Anime adaptations, the animated sequel Advent Children and the Square Enix/Disney mashup franchise Kingdom Hearts. Along with being one of the best villains, Sephiroth has one of the best themes of any FF character. Even the original midi scored version from the game had a real choir singing the Latin lyrics. Now One Winged Angel is the crowning jewel of the Distant Worlds proms.
T - Theatrhythm: Final Fantasy
The newest addition to the ton of FF spin-offs is this rhythm based celebration of the fantastic music of Nobuo Uematsu. Taking the best of the best of FF music and adding fun FF themed visuals and stylus action that ranges from accessible to finger ballet, Theatrhythm: Final Fantasy is a must for any music loving DS owner.