Underwear.

One of those words you can walk up to any 7 year old boy and say and they will bust out laughing uncontrollably. I was at the mall recently with Frodo and my hubby. (Still haven't figured out what to call hubby online yet...) We walk past Victoria's Secret and you can see hubby eyeing the merchandise. Frodo looks at me. I tell him, "It's an underwear store." He busts out laughing. I clarify, "It's a FANCY underwear store." He thinks that's even funnier. Hubby interjects, "It's a fancy GIRL underwear store." And Frodo is practically laying on the floor he has the giggles so bad.

Another word to say to a 7 year old boy to make them giggle uncontrollably: butt.

Feel free to add to the list....