Okay, I may as well defile the rest of my levels as well:
-MILD-
Just Balls
In The Balls Of...
The Balls
Wish you had balls?
Take Your Balls...
On The Balls
On The Other Balls (heh. these two go so well together =P)
Farewell, My Balls
Crying Over Spilt Balls
Balls Not Reccomended
Up To Where Balls Go
Blow Balls!
With A Little Balls...
The Descending Balls Scenario
You Just Lost The Balls!!!
-WIMPY-
Two Balls
(Also they are balls.)
Balls of Despair
Balls, The Universe & Everything (or any other variant of that =P)
A Ball Would Be Handy (heh... or take out the "A" at the start then you can actually use "balls")
One Ball At A Time
Down With The Balls
Get balls, balls, balls!
-MEDI-
Getting Balls...
Balls Blast
Balls of Faith
The Balls of Lemmingsville
Bob's Balls
Balls Up!
All Roads Lead To Balls
Shooting Balls
The Lonely Balls
Six Balls Under
Ghostly Balls
Balls of the Lemming
Balls Up High
Consider Balls...
-DANGER-
Metal Balls
In The Balls of a Lemming
Some Kind Of Balls
Alternative Balls
Unholy Balls
With A Ball or Two
Balls of Wisdom
When Life Gives You Balls...
Balls In All Directions
Circular Balls
Balls Rotation Syndrome
Die the Death of the Balls
Lair of the Fallen Balls
Use The Balls!
So that's the balls...
Deadly Balls
Balls Problem
** EDIT **
And to reflect the latest update that introduces or renames a few levels:
Russian Balls
It's The Balls Craze!