I would choose either Andy Lately or Andy From The Block. I've wanted to change my name to the first for a while and the second I just think is hilarious lol. I wouldn't put a lot of thought into it - I sat here for ages thinking about a good name when I joined PC before I finally landed on Shining Raichu and now I'm not the biggest fan of that name so it just goes to show that thought isn't necessarily the answer :P. I felt my name should be Pokemon-based since it's a Pokemon forum, only to finish joining and find that half the names had nothing to do with Pokemon at all :P.
Now... what makes a good username. Hmm. PLEASE KNOW THAT I MEAN NO OFFENSE TO ANYBODY. IF I DON'T LOVE YOUR USERNAME IT DOESN'T MEAN I DON'T LOVE YOU.
With that disclaimer...
If you have more than one word in your name, I think it looks better if your name has a space between the two words rather than a - or a _ or just merging the words together. I am also a fan of proper punctuation, so I like capital letters at the beginning of each word (though I find this doesn't worry me so much in single-word names like donavannj or bobandbill, the latter of which breaks all these rules and still manages to be the exception to them).
My pet hate in usernames is a tie between unnecessary punctuation (if I see ~*!*^!*& around your username I automatically cringe :P) and numbers. So the best usernames don't have those, in my opinion. I also hate unnecessary x's in usernames (no offense xxReshiramxx I'm sure you're lovely!!!)
Finally, the best usernames are inventive. Ayselipera, Ausaudriel, Sylphiel, Bloodex and Know-Nothing Bozo the Non-Wonder Dog are among my favourite usernames because of this.