I haven't played a lot of your maps yet (you are responsible for Woman Tag and Zombie Mall though, right?), so you may have already beat this concept to death in another map.
HOWever,
I think there's gotta be something really cool you can do with a mini-game that involves:
1 - cloaking or burrowing units
2 - a Detector unit, such as an observer, that is blind
3 - ??? other units?
4 - PROFIT!
Other ideas I've had while playing mini-game party:
1 - a race wherein the racers have the ability to cast Ensnare to slow their rivals and Dark Swarm to make it hard to see the obstacles
2 - Spin the bottle, but the kisser is a firebat and the kissees are zerglings with speed. maybe the zerglings have 0 or 1 damage - the kisser can easily handle one or two zerglings, but he has a small HP pool (like in woman tag), making it risky for him to try to kiss a whole bunch of people in one go.
3 - Some sort of a mini-game where the participants get drunk. I don't know how to represent drunkenness in Starcraft mechanics, though. I recommend getting drunk and walking around your campus or playing starcraft for ideas.
It could be a drinking game type thing, where every time you do something wrong you have to take a drink, suffering the effect(s) of drunkenness more frequently or in greater potency as you get drunker, making it harder to do the game. It could also be a simple thing of, every few seconds your character is a bit more drunk, and that is bad for some reason. Or maybe you WANT to get drunk, so you try to take a lot of drinks, because you win when you pass out, but the drunker you are, the harder it is to successfully walk or fight your way towards the kegs of booze.
BUGFIX - In hot potato, we had a bug where the potato changed hands, and the music kept playing, but the round never ended and the potato refused to change hands ever again. The hot potato was a vulture. We only had teal, orange, and I think red playing. Maybe it was blue, but I'm pretty sure red. (top center player, bottom center player, and a player directly to the right of bottom center) Teal passed the potato to orange, and orange's potato could move up to our flags but wouldn't change color. The music continued for at least 2:00 longer but nothing happened, and we had to RM. I've played minigame party several other times, including two or three other iterations of Hot Potato, and experienced no errors in them.
Have you checked out the humongous game revision known as Ultimate Doom, on Starcraft.org? It's a really ingenious piece of work, as far as game modifications do. It anticipates (and likely inspired) some of the things they've showed us in SC II (notably, Marines in Ultimate Doom can chuck bouncing grenades). You might be able to steal some of the marvelous code from there for interesting effects.
None.