Agent of Shadow?
Agent of Subterfuge?
Agent of Strife?
None of my sneak skills are particularly high. But I went ahead and picked Subterfuge just for the jell of because it sounds fun.
Also, regarding Agent of Shadow....according to the wiki it allows you "to be invisible for 2 minutes while sneaking."....now, does this mean I can sneak during a fight, and actually remain invisible to all or most enemies while wacking them to death?