While that was certainly terrible. It's not the worst ever. Check out these. First up, Carl Lewis, who not only has one of the worst first pitches ever, but one of the worst national anthem's. Here's the pitch (sorry, you'll have to click on this link): http://www.turbobuicks.com/forums/waiting-room/75298-worst-ceremonial-first-pitch-history.html
And now. here's his National Anthem:

Or how about this one from the Mayor of Cincinnati?

Still think Gary's was so bad? How about Mariah Carey? She looks better than Gary while doing it, but her pitch totally sucked:
Mariah Carey First Pitch - Watch more Funny Videos
How about this classic?
Or how about Adam Carolla?