Sometime after Space War and Asteroids, but before color was widespread in arcade games, there was a 2-person vector-graphics game in which you and your friend drove "tractors" around and grabbed little diamonds (or whatever) from a pile in the center of the screen and dragged them back to your base. You could shoot the other guy a la Space War, but I think there were also bad guys flying around to shoot a la Asteroids.
Name that Arcade Game!
Update: KSharkey rocks! He correctly identified Rip-Off -- with graphics like this, it's no wonder I was enthralled:
With the advent of color, there was this game involving a grid of city blocks. A dozen or so triangles started moving from one side (or all sides?) through the grid. I don't recall if you controlled the triangles or you controlled a car trying to get away from them, but over time the triangles would end up crashing into each other and being destroyed. And you either were trying to destroy them all before time ran out or you were trying to keep them alive until you achieved some goal.
Name that Arcade Game!
Update: WillC2 Rocks! Targ it is!
Well, guess I'm going to have to renew my XNA Creator's Club membership...