I've never used a crossbow, but I would think they'd be a bit awkward to haul around as a basic survival hunting tool. Even a small "hand" one (never seen one of those personally, but I can imagine what you're talking about). For emergency hunting use I'd consider a slingshot even better - you'd have basically unlimited ammo using small round pebbles. But a "Wrist Rocket" style slingshot would still too awkward to routinely carry IMHO. Plus, I don't think I've ever been able to hit anything with one. Practice ahead of time would be needed, but I'd still consider this a dubious thing to carry as a normal item. It would depend on your circumstances I guess.