I'd advise against getting UTIII as there are so few active players. Having only one or two active games to join in a given game mode makes you question how much longer there will be people actually playing. If you do get it, let me know when you want your beatdown.

Crash Commandos is supposed to be pretty action packed, like a 2d unreal tournament, and is only 10 dollars/euros on the psn store.

Uncharted is pretty fun and definitely good for a few hours of entertainment.

Warhawk is great fun but definitely not for everyone, so be prepared to die over and over as a rookie. There is a demo of this on the PSN. Do the tutorial.

If you like Tekken, download Tekken 5 DR from PS Store, 1080p 60fps of Fighter Heaven ^^

You should put on deodorant then.

EDIT:  Oh I see Benga beat me to it.

OT:  You are an interesting fellow.  You like "fast paced games" yet you like platformers like LBP... oh well
I would definitely grab Pixel Junk Monsters.  If you like Tower Defense games at all, this one is a must!

try Valkyria C. it s a must, and the demo is nowhere near the final game

Judging PS3 games by playing "demos"??? Yeah, that's so right..../sarcasm

That is exactly the purpose of a "demo"....  to judge the game and determine if you want it.  That just means the PS3 developers need to release better demos.  Demos are supposed to make you want more, but if that isn't the case with these games, why even have a demo?

^therefore, he's bored by DEMOS, not by the GAMES, as his title implies.

BUY LITTLEBIGPLANET

it seems like what you want!

It's not exactly fast paced, but PixelJunk Monsters was an absolute joy to play.

PSN downloads recommendations:

Warhawk
Burnout Paradise
Tekken 5
SSF2 Turbo HD Remix (if you will only buy 1 fighter, get this one)
WipEout HD
Bionic Commando Rearmed
High Velocity Bowling (great, fun and cheap)
Crash Commando (online multiplayer game is best)

If you're into retro-gaming try Mortal Kombat 2 Arcade and Suikoden PS1.