I'll have to say that Rube Goldberg contraptions are awesome.
In what is basically an interactive physics program, Garry's Mod, one can simulate different physics (gravity, even static and kinetic friction) but heck, to put it bluntly, nobody talks about Gmod in those terms very often. But! when you're messing around with Rube Goldberg contraptions very minute differences can make something go amiss.
So here's a video that I really like. Everywhere there are examples of physics. I like the part at the end where the crates slide down a massive ramp. The people at the end are encountered by a massive load of kinetic energy because satrting from higher up means more potential energy and we all know for conservation PE + KE = KE +PE, although I wonder if the creator had to reduce some friction on the ramp. Well anyways, this is some fun fun stuff (to me at least :p). The only limit is imagination! (ha what a hackneyed phrase)