Very common keyboard configuration in first person shooters for right handed gamers. W is walk/run forward, S is backpedal, A is left strafe, and D is right strafe. Combined with the right hand on the mouse to turn the character and look around, this provides a lot of movement options with a minimum of finger movement.

As an example, here's my quake3 keyboard config -- it's completely standard until the 'g' key:

w     - forward
a     - left
s     - backpedal
d     - right
shift - duck
ctrl  - walk
space - jump
g     - taunt
e     - shotgun
r     - rocket launcher
f     - railgun
v     - plasma gun
c     - lightning gun
aww, how cute, I got a learn how to spell softlink. /msg me with the spelling correction if you can find it -- I sure can't