Agreed with Lotus, yoyo's get too big.
Poor khulis wouldn't fare well either. They don't have much defense against a con that may go all "seek and destory" on it.
Skunks are feisty enough to possibly get along with the con. Some people have reported them pestering other fish, nipping the fins and such. Might be ok with a con, even females get huffy every once in a while.