Mantis shrimps don't make clicking noises. They make no noises at all (in my experience). If you're hearing clicking noises, and you've ruled out the fish (e.g. clownfish make clicking noises) then it's either a pistol shrimp or a snapping shrimp. These both belong the same family and the distinction between the two is vague. I've kept coldwater snapping shrimps in their own aquarium and they're lovely animals. Active, hardy, and noisy! Mine seemed to be fairly sociable, too.
Mantis shrimps are even more fun. The only possible problem with a mantis shrimp is having it in the wrong tank. Beyond that, they're wonderful animals. Virtually indestructible, smart, highly entertaining. In my opinion, a hundred times more enjoyable than any coral or reef fish!
Cheers, Neale