Here's one I'll bet few people know.
Place your cursor over either the Viewer or the Canvas then hold down the H key.
You should see the Viewer or Canvas pop out at 50% size no matter what it was originally set to. Why? I dunno, it's probably some function or preference or something I've missed all these years. But it's pretty cool nonetheless and could be handy since 50% gives a clearer representation of your footage than odd numbered percentages, although 50% won't reveal interlacing as 100% does. Man I'm up late.