Relay races! Have them do different combinations of crab walks (or bridge walks if they have strong bridges), V-up rolls, inchworm walks w/ pushup, handstand walks (if they can) etc. also good to do relay races with straddle L-sit walks down the beam with stronger gymnasts.
Any variation of tag where you have to do 5 pushups (or whatever) to get back in the game.
Simon Says with conditioning exercises (or balancing exercises on the beam)
Monkey walks (chin up - walk sideways) relays on the bars or P-bars. Penguin walk relays on P-bars.
A game we play as a team is holding a plank on a line at the end of the floor, while the coach calls out different commands to do in the plank (variations of push-ups, side plank, etc) and every so often they will give the command to run. When the coach says run, you sprint to the end of the floor, run back, and finish back in the plank. The first person to end in the plank "wins" that round. It's a pretty fun conditioning game that is fairly hard at the same time.