I'd recommend
Vektor Storm, a Tempest-style game we played in the Super League recently. It's a little gem of a shooter, and a lot more action-packed and challenging than it might initially look.
Another favourite of mine is
Projectyle. If you take Speedball, add a third player and an obvious air hockey influence you might get some idea of what to expect. It's fun in short bursts against the computer (although it might wear a little thin) but it's a riot with two or preferably three people involved.