Thad has a clip of one of the most famous gags in any Road Runner cartoon, a Ken Harris-animated scene from Whoa, Be-Gone!, where the Coyote tries to... well, just click the link and see for yourself.
Many people consider this the best gag in any Road Runner cartoon. It follows the pattern of a lot of the best gags Mike Maltese wrote for the series, which is to have the Coyote try something really absurd, do a long build-up while he tries to get it to work, and then have it fail for the most obvious reason imaginable. It goes all the way back to a gag in the first cartoon in the series, Fast and Furry-ous. The Coyote gets an ACME Super Suit, apparently expecting that it will let him fly like Superman. He strikes a Super pose, gets a long running start, jumps off the cliff... and instantly falls (he didn't even have to look down first). It's funny because the result was so obvious. It's like Maltese's cartoon-comedy version of Occam's Razor: the simplest result of the Coyote's stupid plan is usually the funniest one.
I think my favorite Road Runner gag is another one in this category, from Zoom and Bored. You get a long, drawn-out shot of a very complicated and elaborate system the Coyote has come up with for rolling a bomb down a mountain. And then he lights the fuse and the bomb immediately blows up on him.
Other favorite Road Runner/Coyote gags?