Dipping it in liquid hydrogen is about the coolest thing I can think of.
...liquid Helium? That's a little bit cooler!
What's awesome and requires PPC on
Well, since you mentioned RTG, I would actually suggest that connecting a BVision and running RTG stuff is amoungst the most awesome things you can do with a BPPC card, at least for a desktop machine.
I don't know if you're an app or a game man (I'm more of an app man myself) but there are a couple of pretty decent games that can take advantage of a BPPC/RTG set up. I used to really love Payback on my A1200 tower machine, with a BPPC@240 and a Voodoo3 RTG card the graphics and effects were truly awesome.
If you're an app man like me, then just running workbench and all your applications with a BPPC/RTG combination is a much much more awesome experience than AGA.
I've never run OS4 on a classic machine (though I plan to once I can get my BPPC cards working again) so I can't comment on what that's like...
AH.
AH.