With the news of the Halo: Reach default controls having the melee button placed on the Right Bumper, I realized that the last major holdout reason I have for using the claw didn't exist anymore. It's likely I'll revert to the old Halo control scheme, but at this point it's simply because I associate The Claw with my 360 controller, and my hands are stuck that way with almost every game. Most controller schemes simply seem to be built with death-dealing accessibility in mind, so the biggest advantages to it are lost.
For those unfamiliar, The Claw consists of holding an Xbox or 360 controller with your right hand set up thusly: Right thumb on the right analog stick, right index finger manning the face buttons (bumper optional), and right middle finger keeping the trigger a twitch away (bumper optional).
As an extra, non-FPS example: Need for Speed Underground's Drag Racing mode was fantastic with a Claw setup. You can keep your head on a swivel to make sure no-one is about to and overtake you, be ready to shift with the face buttons when prompted, and keep that accelerator floored.
Also, while growing up I knew a kid who used an N64 method everyone around here called "pinching," where instead of using a thumb for the analog stick, he pinched it between his thumb and forefinger. If using the Z trigger, he would reach underneath with his right hand and tap it that way. He could kick my ass at Smash Bros., so I never questioned it. He returned the favor likewise after I had naturally began using The Claw with Halo.
So what goofy ways do you hold your controllers? Do you associate it with certain genres like First Person Shooters? Is it on a game-by-game basis, or perhaps just every game?