Algodoo

Probably the best thruster I've ever made.

I get 131.8 m/s from this craft (and it's tiny!), which makes it by far the best out of all my propellant engines.
It uses some lasers and attractors to accelerate the exhaust to around 30 m/s.

Honestly, it's not the most reliable: A lot of the time the propellant will misfire and it'll lose velocity. Overall still pretty good though.

WAD to control.