I love Smash TV! - One of my all time favorite games. I got mine from Exidy via these forums, and later added a TC board with Mike's Jamma switcher. It's THE best two player cooperative game out there, and really encapsulates the ultra-violent/commedy combination that dominated action movies of the 80s/90s (Running Man / True Lies...all that).
I do relate to the folks here who call it a quarter muncher. It really is the supreme continue game. In late levels you're just constantly dying. To keep it interesting in an unlimited credit home setting I think you have to develop your own challenges. I like to try to beat the first screen without firing a shot, and finish the first level without dying. Both of which I can do regularly.
I also push for highest possible score, which is done by playing one player games, but always having the second player on the screen, which increases the number of enemies.
I know I've read that the game developers stated they could finish the game on one quarter. To me it just doesn't seem possible, but who knows.
As I play I'm always thinking:
Kill Purple guys before Green
Never stop firing and never let a bullet hit a wall
Most under-rated power-up = the shoes. I always go for them first.
I love the phrases that occasionally pop up between levels. "Chunks Galore!!"