5 essential applications for good gaming

[Sp4]

Uh 5.. okay, I'll try to name 5 that I use.

Steam, TS (probably the most important ones)
Hamachi
Something to listen to music with (I use winamp)
Can't think of a fifth one buy I'll put Skype because if I don't use TS, I use Skype ^^

Oh nevermind, I didn't read which kind of applications you meant.

I use CCleaner, not sure if it helps, I got into the habit of using it a few years ago. It sure looks satisfying when it says yay I've deleted 500 MB of useless crap!
Not sure if it counts as application, but a disc that lets you wipe your hard drive in case you break it. I use this like once or twice a year. Yay utility gaming computer lol.