I've killed garden slugs with an air pistol, a mockingbird with a rock, squished thousands of ants on the sidewalk with a rubber ball, sparrows in the shop with an improvised blowgun, hunted bumblebees with a switch (bad idea, they can fight back), and blue crabs in an estuary with a .22 rimfire. The crabs are excellent to hunt - they are wary and fast.
I bowled a squirrel over with a baseball sized rock one morning, but it didn't seem to have much affect, except you couldn't get within a 100 yards after that.
The best was hunting rattlesnakes at Michael Field, Utah - with a fishing pole. After the first TDY there, someone got the idea to take mouse traps and a bait casting rod on the next trip out. The idea was to trap mice out of the shack, truss them up alive on the end of the fishing line, cast them into likely looking rattler country (that would be anywhere you could see), then slowly troll them back hoping for a strike where the snake would hang on. Old habits of setting a hook are hard to break, and I don't think we ever got a snake back, but it was something to do.