My watch of choice is situational depending on the map and depending on my enemies. My main choice is the C&D, Ambassador (Love this gun) and Knife. I switch to the DR at times, infact in my new vid so far I have a ton of DR moments
Definitely Ambassador (I love teh headshots, if you get a headshot on a sniper you can then just shoot him once more in the chest and he's dead (faster than your double headshot method frisky )), Dead Ringer (ftw, in a pub (aka not eGO server) I can get seven or eight deaths the whole round and thirty or forty kills, cures eGO and its excellent spy checkers!)
For sniper its very situational, although its almost always jaratee I'm using.
Spy:
Normal Watch
Normal Gun
Normal Knife
Normal Sappers
I never found the new spy stuff useful...I can see how it can be used in many different situations...but I can use the normal watch just as well in those situations...
Sniper:
Sniper Rifle
Jarate!!!
That Big Knife
I use the Huntsman when I feel like going Rambo and switch to the smg when I miss using it