you guys should also try aftermath, it's kinda like L4D2. The controls are good but after you get used to the controls you'll never let go of you iphone/ipod.
Bug Heroes Seriously though, for a quick fix I still go back to mini gore... Aftermath was pretty good too.
looking forward to trying Meow Meow Happy Fight tomorrow. But my votes go to Isotope and Meteor Blitz. Pew Pew 2 is also excellent for it's music and no-nonsense, no-fat level design.