Might look into Portland or Seattle as I haven't been to the NW.
Vegas in early December should be pretty dead, right?
I've had my fill of the GOM this year so I don't want to do a cruise.
How about Denver? Is it easy to get around without a car?
NW is great, I would say Seattle over Portland though, Portland gets snow (Seattle can but when they do the city shuts down), plan on 40 degree days though.
Vegas is booming all year round, there is stuff to do even if you don't gamble, but for me I get bored there after 2 days.
Cruise's suck.. it's floating around in your Hotel.. yawn
Denver you will want a car. December is total hit or miss for temps here, I've seen it be 60 degrees then -11 the next week, September is Colorado's best month.
I don't have many ideas, but here goes
Ft Lauderdale or the Key's - Scuba/snorkel/surf sports/golf
San Fran - Alcatraz at night/trip to Monterrey/many city activities
Don't know if you are willing to go international but Costa Rica is amazing, motorcycle tours, eco adventures, water sports, CHEAP