I've been thinking about the possibility of a weapon that damages a ship, then keeps going to do more damage later. I've figured out how to make a homing weapon hit a ship, go through, then come around and hit it again.
The first stage weapon has a proximity radius and blast radius larger than the distance weapon travels in a single frame (e.g. If a weapon's speed is 1200, then it travels 12 pixels in a single frame. Radii of 15 are possible for this, but I use a prox radius of 35, and a blast radius of 40.)
This submunitions into a second stage weapon that has the same speed and blast radius, and a prox radius 10 pixels smaller, and a proximity safety large enough to carry it through the ship. Tack on recursive submunitions for fun.
The end effect is a torpedo that passes through a victim again and again, doing damage with each pass.
I have noticed that larger targets (Think Pirate Carrier) tended to foul the process, producing no submunitions. Smaller ships, however, will be victimized almost systematically.
When I was talking about this with my brother, he came up with the topic title.