For work, I usually turn to my semi-serrated Ka-Bar USMC. No special reason -- just that it was one of my first knives (purchased back in 1996, if I remember correctly) and it was the knife I chose to abuse. Since then I've used it for everything from throwing to splitting wood (with the aid of a hammer). It's pretty battered -- the spine has hammer marks all over it, the guard has been bent and straightened so many times that it's a kind of continuous sine curve and the buttcap is a bit wobbly. The blade's still sharp though.
However, in recent times, the knives I handle most often are my throwing knives -- one large Hibben knife, two medium ones and a Muela Pro-Throw.