Watching Adam Sandler yell "Talk to the doc!" in The Meyerowitz Stories made me realize that he's my favorite in terms of freaking out and yelling. He does it with such conviction. I love it. He sort of reminds me of Sam Kinison in that regard, who would yell and scream in his stand up sets.
So who is your favorite yeller? Or what's your favorite yelling moment or scene? It can be someone that yells a lot in various roles, or something that's only yelled once, etc. Anything. The funnier the better, but it doesn't necessarily have to be funny.