Well pretty much any bottom dwelling fish (Plecs, loaches, cories etc.) will probably be food in short order. Fish that inhabit the upper waters stand a far better chance of survival, however ultimately they'll probably end up as food also.
A crayfish is often best kept solo or with fish your not terribly attached to (or fish your currently mad at....different story) I had a blue cray, he pretty much destroyed everything I put in the tank, it was just his nature, my brown "feeder" cray was also this way. However some people have kept crays with fish rather successfully, so I think it boils down to the specific cray in question.
Sum it up? If you like the fish.....the Cray probably will too