We abandoned testing nuclear rocket designs back in the early 70's. If I remember right there were issues with shielding the motor because it would spew radiation all along its flight path.

What I'm still waiting for are kamikaze drones. Imagine something like a predator drone that can stay airborne for a few days before you want to strike, then safely piloted to its target by someone in a nice airconditioned room. Basically WWII Kamikazes without the pilot having to commit suicide.