Couldn't quite answer all of them, but here's from my expereince:

Best plot twist: Deus Ex
Worst plot twist: I'm going to nominate a movie: The Leauge of Extraordinary Gentlemen. Moriaty? Otherwise the movie was good! <img src="/ubbthreads/images/graemlins/delight.gif" alt="" />
Best fight: Doom I & II
Best city: GTa2
Worst city: Most small villages in RPGs. Please will you have some character and not just a store, healer, sherrif and a save point.
Worst NPC: Black & White: The wanna-be sailors. Won't they shut up?!?
Best weapon: American McGee's Alice: Jack-Bomb. It's like a garden sprinkler, only with napalm! <img src="/ubbthreads/images/graemlins/delight.gif" alt="" />
Worst spell: Healing in many RPGs. What's the point when you have 200 healing potions?
Best skill: Deus Ex: Ocular Enhancement
Worst skill: Divinity: Traders Tongue. There's enough gold in the game as it is!
Most hated NPC: Janus! <img src="/ubbthreads/images/graemlins/delight.gif" alt="" />
Best quest or sidequest: Neverwinter Nights: Charwood Forest
Worst quest or sidequest: Please collect this package from the guy on the other side of the world and bring it to me.
Hardest game to beat (boringness doesn't count): I don't know. Too many I haven't beaten! <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />