Some of these are either too intricately difficult or encourage bad tactics. Still, I like the idea of acheivements

A few ideas for achievements:
Stab a heavy and his medic
Kill someone with a revolver immediately after uncloaking
Kill someone attacking your autogun while it is being built
Touch the intel immediately after someone else caps it
Kill a rocketman after he propels you in the air with a rocket to the feet before landing
Burn a sandwich eating heavy
Use x4 100 times?