Eschewing Formal Language

Would you write "The worst tennis player around here is I" or "The worst tennis player around here is me"? The first is good grammar, the second is good judgment.
--from Strunk and White's The Elements of Style.

I wouldn't write either. Both suck, both sound pretentious and both cause the reader to stumble and break stride.

When you're going over a first draft of something you've written and you find yourself staring at a sentence like this, please have mercy on your readers. Break out your red pen, annihilate the offending text, and start over. Just a few seconds' thought will bring you to an obvious substitution:

I'm the worst tennis player around here.

Or better still, the even tighter I'm the worst tennis player here.

Match your language to your audience and medium.