i remember this one time a neighbor was burning ants and he pulled out some gasoline and he fucking tipped it and a gallon of gas dumped out, pouring under his dads car. the whole thing torched up. higher that the telephone pole. it was the funniest shit. then when the fire truck came, it drove right passed and somehow didn't even see it. it wasn't a prank, but i just got reminded of it.
as for pranks...
-superglue and toothpicks in doorlocks. you cant fix it. you need new locks.
-bleach in the detergent is funny, but you can also put fixer for developing film in and stains clothes black. you could also use dye.
-i remember leaving through fire exits and setting off the alarms. then they'd evacuate the mall and send fire trucks and shit.