The Kevlar Cadaver (man I want to spell cadaver with a "K") doesn't quite live up to his potential. He has a very slow fire rate with his pistol. Thankfully he doesn't know about the M16 on his back with full auto capabilities.
The Cadaver is immune to Insta-Kills due to its heavy body armor. Don't get excited though, because by the time you are through killing him it will be worthless.