Intro: Allow the spade to be thrown.
Details:
Basically if you are completely screwed, you can throw your spade for an instant-kill, but lose the ability to dig.
The spade would be affected by gravity and travel slightly farther than the grenade.
Could be implemented in a variety of ways, such as using the middle mouse button, a keyboard button, or even as a new weapon.
Benefits:
It would be a good last resort weapon that would fit with the theme of the game and be a substitution for a pistol.
Drawbacks:
Might make the game too close to Call of Duty for comfort.
I know throwing knives have been suggested before, and this was one of the arguments against them.