I like a Cman which gives ambushers extra precision with specific regions, kind of like wspec'ing only it's expertise to an area of the body. So, you might train in head or leg crits. Coupled with wspec, you might get a special bonus if it's slash, puncture, etc. It's a boost maybe slightly +2 or something to AS and a big mod to ambush success and crit factor. It's good for open ambushers as well.