Spin around and shadow box ala Fedor & Co.
Wobble boards (more for balance).
A stepper- step-knee, slalom jumps, step-up-down, rotate 45, step-down, etc.
A new one I've being playing on the heavy bag:
Keep your hands up, shuffle back and forth between orth. and South-paw. Have someone say "2 punch" or "Teep, knee" or "roundhoues"...then the side. If your in southpaw, then you might do a jab-cross, but if the person next to you is in orthodox, then they'd do cross-jab.
If its "LEFT...teep-knee" then same thing. The idea is to simulate being off balance or coming out of a clinch and seeing an opening. Instead of shuffling feet (and losing that split second advantge) just throw from wherever you are.
Got the idea from watching Bonjasky when he does that triple shuffle and then throws that kick in his HL vid.
Hope my explanation makes sense.