noname2200 on 05 July 2009
I was going to suggest Bomberman Blast and Bit.Trip: Beat, but you already own those. 
Let's Tap is a good party game, but you'll need four solid and separate surfaces to play on, which can get tricky. I haven't played Bash Party, but the original was a great party game and Bash Party is supposed to be worlds better. I'd got with Bash Party myself, but you can't go wrong either way.
Also, you may want to consider Defend Your Castle and/or T.V. Show King/ Target Toss Pro. Problem is, they're all almost exclusively local multi titles, so if you don't plan to have such get-togethers often you may want to skip it.
