Bass: The better I get, the less I feel able to classify my skill level. I call myself semi-pro; my originals band is turning a profit, and I'm trying to get a wedding band really going after a few good gigs. I also receive more than just friendly compliments from other bassists and musicians. So I must be at least middling.
Trombone: Used to be quite good in an orchestral setting. I could even sight read, but lost it after years of not using it. I bet I'd have a good ear for trombone if I picked one up. Man, I gotta go look at used trombone prices....
Guitar: You need barre chords at tempos from ballad all the way up to speed metal? I'm your man! You need finger picking or intricate lead lines, or anything based around open chords? I am NOT your man. I've played rhythm live, no problem. I even throw in some Chuck Berry riffs when appropriate.
Drums: I'm working on it! I can handle your average AC/DC song, but if it's not in 4/4 I get lost almost immediately. I'm better at double bass than my main drummer, but he's an utter stud at anything else. So, I'm still better than Meg White. Does that make me pro-level?

I hope to be at a giggable level with drums in a few months.
Keyboards: Bloody awful. I have a decent keyboard in my jam/practice room, and I play around with it once in a while, and I make myself depressed with how awful I am.
Vocals: Good. More than comfortable enough to sing popular songs acapella impromtu in front of a crowd and not fear laughter or mockery. So I must be good. For a while, I even considered myself more of a singer who played bass. Now I'm usually too busy playing to sing.
Cowbell: I learned from the master, Gene Frenkle. I'll bury anyone in a Battle of the 'Bells.