i have found many fun tricks, though some may be slightly mean, some where taught to me by my cousin..
1) Tell a gullible person that is at your house for a swim party that the bottom of your pool smells like strawberries (please dont try this one it can be dangerous)
2) tell somebody to put there hand right infront of their face and go to the mirror, tell them that if they cant see themself in the mirror that their hand is bigger then their head so they have a terrible desease (make up name)
3) hold out your hands with your fingers spread, count them saying the number 8 after each one like this, one-eight two-eight three-eight, but when when you get to the 8th finger skip it, and it will sound right, trust me.
4) tell somebody that their water might be polluted (put in some foodcoloring, barely any) that is inside their cup tell them to keep sniffing it until they smell somthing wrong with it, let them sniff for a while, then behind their back get anything with a strange smell (anything) they should smell it and beleive the water is poluted.
Those are the tricks, number one can be dangerous, people feel free to add on to the list, i think we would love to see some funny ones
I do have one really gullible friend, and once I was walking behind her when we passed an open window, and I looked out and said "Oh look, a unicorn!" and she immediately turned around and ran to the window next to me saying "Where?!" before remembered unicorns don't exist!