Not to be a killjoy or anything, but I'd avoid the stink bomb stuff.
Especially these days with all the terrorist crap and student shootings. You could find a swat team descending on your parents place one morning.
Not to mention, if one of the students has bad asthma or is alergic to any of the chemicals you're using you could be looking at a hefty lawsuit or even murder charges.
I'd stick with the penis jokes.