Originally, in the 1990s, I didn't know any better and just used the keyboard. Arrow keys, left and right = turn, etc.
Later on, I eventually adapted WASD + mouse and suddenly became much more proficient as a result.
However, around the time I was first exposed to Tribes 2, I started using ESDF and sticking with it.
Yes, it's a pain in the ass to have to remap just about every game out there to use ESDF rather than WASD (and some titles, like Hostile Waters, don't even let me remap the damn keys!), but having Q, A, and Z off to the left for other functions helps a lot in many games with tons of keybinds. And, besides, I'm a control freak and won't be happy unless I've got my controls configured EXACTLY how I want them.
Anyway, general keybinds:
ESDF: Forward/Strafe Left/Back/Strafe Right (of course)
Space: Jump
Left Ctrl: Crouch
C: Prone
Left Shift: Sprint/Walk (for older games, I just leave autorun on)
R: Use (in cases where W and R are used for other things, I'll map it to G instead)
W: Flashlight/night vision
T: Global talk
Y: Team talk
Left Mouse: Primary Fire (of course!)
Right Mouse: Secondary Fire, Grenade, Zoom/Sights, Melee (in that order, depending on the game in question)
Middle Mouse: Reload, Inventory Use
Mouse 4/Thumb Button: Grenade, Sights, Melee, quick mouse menus like in BF2 and Crysis
Mouse Wheel Tilt Left/Right: Inventory Left/Right, Grenade Switch/Weapon Fire Mode
That's just the tip of the iceberg; many of the other keys have myriad uses between games that generally don't carry over.
