My favorite use of them was to replicate a reactor core detonation. I have a ship called the
Mariner where the reactor core can be jettisoned. The reactor will explode shortly after ejection, so you'll want to make sure you're not near it when it goes up. It would've been nice if there was a way to expand the explosion radius. I'm not certain how well the ship will function now with the advent of the auxiliary blocks...
I've also made torpedoes to give some of my really small ships a little extra punch. Replacing them after launch is a hassle that doesn't appeal to me. I'm looking forward to the day they introduce flagships, though. I want to see if I can make a system that actually builds a torpedo using stored material, loads it into a tube, and launches it.