Ive long maintained that a decent 4-way GC fest while pissed is one of the best ways to spend an evening.  But Ive played most of my games too much so Im in search of something new.  Between me and my mates weve already got the following:

>Smash Bros
>Timesplitters 2
>Mario tennis
>Super monkey ball
>Mariokart doubledash
>Metroid prime
>James Bond Nightfire

Of all of these, we play Nightfire most of the time (despite it getting rubbish reviews) as its absolutely fricking amazing and more than a match for Goldeneye on the N64.  Everyone says it isnt, but sit down with the two side by side for half an hour andI promise you wont look at the N64 again  Monkeyball gets played the rest of the time usually, thats wicked fun.

So what else should I get?  Ive heard bomberman and smugglers run are supposed to be quite good on multi, any opinions?  I dont really care about the singleplayer aspects of the games as I have a PC for that stuff  

Bomberman is always good!

I only really play Smash Bros on mine multi

Mario Party.

Yeah Mario Party 7 is fantastic. It comes with a small microphone for voice recognition, which i must say works extremely well. The games are hilarious and certainly a great party game for cute fun... just in case you get fed up of shooting eachother to death in Nightfire.

Yer the Mario Party series are good, I mainly play the mini games. Can be a right laugh surprisingly.