Change one letter in a game's title and you get....

[whaleswiththumbs]

Left 4 Dead becomes Left for Dean.

Because no-one likes Dean.

Wouldn't they be leaving for Dean though?

OT:
I don't know if its already been said, but Half Life becomes Hall Life, which would be the most accurate simulation of a guard in a totally normal day of work ever.

EDIT:
I'm thinking of another one incase of NINJAS!

Spore to Smore? Camping simulator.

 

[Sporky111]

Scribblenauts -> Scrabblenauts :: Save the cosmos with the power of seven-letters or less words

Myst -> Cyst :: A hospital-sim

 

[cryogeist]

rainbow six vagas
becomes
rainbow sex vagas
dont report me

 

[Recron]

Little Jig planet - create ad customise your sackboy and have them so a little jig in over 2 milion user created levels
pokermon - Gotta catch em' all, for a game of poker.
D Zero - got a higher grade than F Zero
earthfound - play an incredibally short game about a psycic boy on his quest to find earth
kirby's epic Barn - side scrolling adventure with farm animal related powers.

Edit: Just cme up with some more
Mischief Fakers - you think they're up to no good, but they're not
Half Lie - stretch the truth!

 

[Scobie]

DELETED

 

[Theron Julius]

Dead Pace. You go through the entire game at 0.1 mph!!

 

[miscelaneous]

Scribblenauts -> Scrabblenauts :: Save the cosmos with the power of seven-letters or less words

Myst -> Cyst :: A hospital-sim

I think has to be the best.

 

[Sgt AssHead]

Duke Nukem: ForNever

 

[Raziel_Likes_Souls]

i know this is just adding a letter but :resident evil becomes resident evil, oh god the presidents a zombie!

I'm Canadian, lol!

Yes, Harper is a zombie.

Total Overdose becomes Total OverDOS. Play through shooting gameplay on our Mexican OS.

 

[kevinsux909]

I don't know if it has been said already, but Rainbow Six makes the controversial "Homosexual Hot Coffee" game, Rainbow Sex

 

[=HCFS=Discoman]

good sir, that is quite good

 

[Kyman102]

Mass Effect becomes Bass Effect, the greatest fishing game ever!

I was going to try and come up with something, but... Dammit, I've got nothing that can follow that. You win good sir or ma'am, you win. *Starts clapping*

 

[Are.Oh.Why]

Super Bario Bros. now they're Mexican!

 

[PauL o_O]

Call of Dfty.

amidoinitrite?

 

[Romblen]

Mass Effect becomes Bass Effect, the greatest fishing game ever!

Or the best Guitar Hero knock-off ever!

Call of Juarez: Bound in Blood becomes
Ball of Juarez: Bound in Blood
It's a western soccer game, where the players can only use their revolvers to move the ball.

 

[AgDr_ODST]

Moss Effect: the game where all the ships and people move as fast as moss grows(in real time). It'll take you 100 years to complete this game
Team Fartress 2: 9 classes, and a ton of guns that stink
Sod of War: this fertalizer means business
Twisted Petal: flowers drive around pots on wheels trying to kill each other
Trials MD: try to speed your way through a number of increasingly difficult days as an on call doctor

 

[tthor]

Gears of Car= an educational puzzle game designed to teach you the fundamentals of auto repair!

Mount and Laid= +18

Pyro= you play a crazed pyromaniac who likes to set anything he can on fire! He will also steal your jewels.

Legend of Zelda: the Wind Breaker= Do you smell something?

PokeMan= +18

 

[Walkchalk]

Final Pantasy, the quest for the last pair of pants in the store which has unlimited pairs of pants

 

[EPolleys]

Mass Effect becomes Mass Erect