The fun, wobbly character of Jello, as well as its inexpensiveness, makes it a hit substance for scantily-clad nightclub wrestling. You don't have to have a sploshing fetish in order to enjoy watching people rolling around in jiggly, wiggly Jello! But if you do, it's doubly fun.
The problem with Jello is that it quickly melts back into colored, sugary water once it warms up--which happens quickly when people are in it. And for the time that it is still cold, it is uncomfortable to be in. It also has the potential to stain skin and hair.