We bought some cable protectors after Buster chewed the telephone wire in half :roll:
Ours are just wrap around and we then sprayed them over with Chew Stoppa from P@H (not sure if this works with all rabbits but Buster sure doesn't like the taste!) and I guess he could get through them if he tried, but he is more deterred now. Buster prefers really thin wires, and with the protectors on all our wires are really thick and solid, so they're not as fun to chew. I know you can get much sturdier ones as well if they're determined!