Change 1 letter in a video game's name

DOOM—You don't have enough RAM to run it anyway

Lift 4 Dead—Dead lift simulator

Half-Lift—Valve really likes workout simulators

Age of Umpires—A baseball-oriented time travel adventure

Cunter-Strike—All about cunt punches

Bump

This Bar of Mine

Control 4 bartenders throughout the day and night to serve the customers. Don't let drunks wreck the tavern, manage emotional situations, and learn people's lives.

Child of Eight.
It is your 8th birthday! Invite your friends and play with them to all kind of fun games. But be careful, the animatronics in this pizzeria are really scary D:

Alan Lake

A Dark Presence stalks the small lake of Bright Falls, pushing Alan to the brink of sanity in his fight to unravel the mystery and save his love.

Mimecraft - In this game you play a mime who acts like he is mining, crafting and building stuff.

Another Word: anniversary edition

Scrabble . it can be X-rated if you really want it to be

Half-Life 3 - a simulation game where you seek for the unstable lithium isotope.
Ass Effect - A game about taking care of unforeseen consequences of donkey breeding.
Bat Rats - game about defending yourself from the rats with only a baseball bat.
Need for Speed: Pot Pursuit - Game where you play as an addict trying to get his next his next fix.
Typing of the Dad - a game where you play as a father writing letters to his son in the different stages of his life.

Super Teat Boy, he can kill things by rolling his fat and producing shockwaves, or by choking them to death in his moobs.

Bump.

Limbo - Bimbo
I think it's self explanatory too xD

FTLD-Roguelike in which you must become the greatest online floral-delivery retailer by upgrading your delivery van, flowers, and destroying the competition's delivery fleet.

Warhammer 40,000: (F)Armageddon:In the grim darkness of the future there is only growing sustainable crops!

Deus Ex: Invisible Wall - a cyberpunk tunnel based open world universe where all loose story threads are neatly wrapped in the end by a scripted plot device out of the players reach. (ok, 2 letters, but my mom told my I could)

Bump

Wither 3 - You plant a tree and watch how long will it last without watering. It's the third part of this popular franchise. Now you have huge open world - lots of places to plant your tree. From mountain peeks to the bottom of the ocean.

There are a couple I keep seeing the first time every time I read the game's name (note, the second one doesn't strictly follow the rules, as it's two letters added).

Immoral Defense
A tower defense game that pushes your ethical boundaries and asks how far would you would go to defend your base.

Contraception Maker
Construct complex Rube Goldberg machines designed to prevent pregnancy.