I used to have one heck of a lot of fun playing a little game called Bratwurst. It's a 2D vector space shoot 'em up. Only downside is that it's for 2 or more players....but probably the most fun I ever had on any two player game, besides perhaps The Chaos Engine, or maybe even Hired Guns (that's good for 1 player as well).
http://m68k.aminet.net/package/game/shoot/bratw101I'd also check out Sidewinder. It's another game similar to Banshee & Swiv, so you may like to try that one too.
