Virtua Cop 1 and 2
Fantastic games. With a little thrifty shopping you could get both plus a light gun for around $30 - 40
Panzer Dragoon and Panzer Dragoon Zwei
These games are sometimes overpriced, but if you wait it out you can get a good deal. Sometimes the JP versions are cheaper and if you can play imports, they play just the same
Winter Heat
A fun arcade-style winter olympics game. The graphics are surprisingly good and so is the gameplay.
Sega Rally
A good game that you can pick up and play, have fun with but will take you a couple of hours (at least) to really master.
Galactic Attack
A vertical shooter, otherwise known as Layer Section in Japan. Good graphics, good gameplay mechanics and usually pretty cheap.