All of my favorite pranks are ones perpetrated over the years by students and/or faculty at Caltech. I actually have Legends of Caltech, a book documenting many of the school's well known hijinks, somewhere and it saddens me that I have not been able to locate it for a number of years.

So as not to go through the difficulty of rewriting or even repasting some of the pranks, I shall simply link you to some pages below.

http://www.museumofhoaxes.com/hoax/Hoaxipedia/Great_Rose_Bowl_Hoax/

http://en.wikipedia.org/wiki/California_Institute_of_Technology#Pranks

http://mighty.caltech.edu/~prank/

http://www.legendsofcaltech.com/