I pretty much always use my Strange Dead Ringer now, but some of you may remember that I used to use the Invis Watch exclusively. It is still my favorite watch; nothing feels better than perfectly sneaking up on the enemy and getting a great pick. However, for 99% of the time in public servers the Dead Ringer is a better choice. The Invis Watch is better against organized teams or teams with 1 or 2 specific targets (e.g. a really good Demo, a Medic, a troublesome Engi nest).
And yes, the Enforcer is a bullshit weapon that's only OK to use if you're having a really bad day. Otherwise I think every Spy should learn how to use the Ambassador effectively. The stock revolver is fine too, although I think the Amby is way better once you start getting regular headshots.