Ancistrus species might work or otherwise some mollies of big enough size to not get caught. Red line torpedo sharks might also work just might be a bit boisterous for the crayfish or overall style of your aquarium.
I've kept them with cories and bigger tetras; I'd avoid anything really small, like neons, embers, or any microrasboras. The only fish I've ever lost to them have been the weak ones that already weren't doing too good. Also, be careful with shrimp. I did keep neocaridinas with mine and they never seemed to bother them, but they most definitely did pick off any and all shrimp babies. Honestly, if they weren't so well-fed I'm sure they would've made a meal of the adult shrimp too!
Edit: BUT, take this with a grain of salt. What works in one person's aquarium might not work in another's. It all depends on your conditions and the temperament of the individual specimens you keep