I use military embossed style ones.

I find anything else i've ever used just gets rendered illegible by the kind of things my dogs get up to.

Very true.... In the last two weeks alone I have pointed out to several dog owners that they are techically breaking the law by not providing a tag with the correct details on it.... one guy was walking his dog offlead and no collar on the dog by one of the busiest roads around here... made me cringe I had to say something. Whats more, after i had spoken to him, the police pulled him over for it too!