A lot of these drills sound like skiing to me. Just going off of the OP's question, I'm picturing stuff you can do on the flats or green trails that let you know you can just go for it.
So I'm thinking - skating, whirly birds, javelins
If we are sticking to maneuvers on the bunny slope or very low pitch green trails, then flat 360º spins definitely should be on the list. They require finely tuned fore-aft balance, edge control, total body control on a minute scale, outside ski to outside ski transfer, and sensitive proprioception of the ski-snow interaction.
Here's a list of bunny slope options mentioned so far in this thread. I may have missed a few.
It should be noted that all of these are harder to perform at very slow speeds without the help of momentum, so actually doing them
on the bunny slope makes them more revealing of skill level and versatility.
--skating
--railroad tracks
--outside ski turns (carved)
--pivot slips
--flat 360ºs
--ultra slow parallel (thanks
@Bad Bob for that one)