Twanalyst.com gives you a free Twitter personality test. As always, take it with a grain of salt but it’s a fun thing.

I have done it and got this back:

Personality: renowned inquisitive cautious
Style: chatty academic
BOFFIN

I disagree with boffin but the rest seems pretty accurate. You also get some tweeting tips, mine were:

Your tweeting is already tip-top! No improvements needed – but check back here every so often to make sure your reputation is being maintained!

I notice that when they calculate tweets/day they simply take from when you signed up until current date. In my case that does not make sense. I joined in April 2007 but started tweeting seriously in January 2009.