Here's some more:

A farmer in the field with his cows counted 196 of them, but when he rounded them up he had 200.

Quick one liners:

I accidentally gave my girlfriend a glue stick instead of chapstick. She's still not talking to me.

I broke up with my cross eyed girlfriend. ...
I thought she was seeing someone else.

Capitalization can really change a sentence. For example:
I love to eat candy.
I love to eat capitalization.

I started carrying a knife after an attempted mugging a few years ago. Since then, my mugging attempts have been a lot more successful.