Perks Stalker listed work well. For a sneak though, i suggest: MC, EMC, SS, BC, SR, RBtE, BRoF, and HtG. Not exactly how i did mine but maybe how i'd do mine next time.
The thing about deciding on perks is...you have to really think about how you intend to use this char, and then have some vision about how best to prioritize what's most/least useful for that exact use. I had a very specific plan with mine and using sneak was integral. I had to let HP and DR go. The idea of being great at 2 things is tough (marksman and sneak) so trying to be 3 things (with high defense or speed) is too far out of reach. No single character can be everything - we all have to choose...
* High Speed (BRoF, Action Boys)
* High Defense (Lifegivers, Even Tougher)
* High Damage (BRD, Crits)
...and the more hybriddy you are, the less effective for a specific use you might also be.