My computer.

[nsanexer0]

Well back in the day memturbo was the shit.

Right now I'd have to say syscare from the people that make gamebooster, it has a tab with all kinds of extraprograms.

For performance it really depends, everyone once a day I usually deep scrub mine (uneeded once a week should sefice)
Sometimes ram gets fragmented but not as badly as a harddrive does, it's not significant and if you have it auto-defrag while your doing other things (theres an option in most of them) it takes alot to process the cleaning... so your losing performance and bottlenecking for no reason.

IMHO, you don't really need it alot... but it's nice to clean it up every week or so to ensure performance.