I love Team Fortress 2 partly for the insane number of quotes in game that never fail to amuse me (excuse the strong language):
Sniper:
"Feelings? Look mate, you know who's got a lot of feelings? Blokes that bludgeon their wife to death with a golf trophy."
"Professionals have standards. Be polite. Be efficient. Have a plan to kill everyone you meet."
"Wave goodbye to your head, w*nker!"
"Thanks for standing still, w*nker!"
"One sniper to another mate! GIVE! UP!"
"Everything above your neck's gonna be a fine red mist!"
"I'm gonna blow the inside of your head - all over four counties!"
"GAWD SAVE THE QUEEN!!"
Demoman:
"SO! All ya fine dandies so proud! So cut short! Prancin' aboot with ya heads full of eyeballs!"
"I'm a grim bloody fable with an unhappy bloody end!"
"Oh they're goin' ta have to glue you back together...IN HELL!!!"
"What makes me a good demoman?? If I were a BAD demoman, I wouldn't be sittin' here discussin' it with ya now would I?!"
"They're goin' ta bury what's left of ye in a soup can!"
"In yer language, eat lead, laddies!"
Soldier:
"You will stand next to that cart or I will STAND you next to that cart!"
"This is my world. You are not welcome in my world."
"Godspeed, you magnificent b*stard."
Merasmus:
"Run fools! Run from Merasmus!!"
"MERASMUS ARRIVES ON A TIDE OF BLOOD! Oh hello Soldier..."
"RAIN OF JARATE!! MERASMUS IS...so sorry about this one..."