Three pirates
Scissor me timbers!
Chuck Norris.
Summer...Her name's summer.
3, duh. (My ex's 9 year old little sister told me this joke, and followed is up with: "and YOU'RE the math guy!" >< Burned.)
The finish line at the Boston Marathon.
my girlfriend who's a high school teacher heard this from a student the other day) Q: What do you call a cow with 3 legs? A: Lean Beef Q: What do you call a cow with no legs? A: Ground Beef Q: What do you call a cow with 2 legs? A: Your mom