I second the shimano QR's. Been riding singlespeeds for over 10 years and never had anything slip. EVER.

I clamp it down tight and am currently running 45/16 & 42/19 and have climbed some steep inclines where I was *crawling* up the hill, such that it probably would have been just as fast to walk my bike up the hill.... and it still did not slip. Have mashed off the line and nada.... no slippy.

I have used salsa QR's on my singlespeeds and they do slip a little. The holding ability of a knurled aluminum QR just does not seem to work as well as a steel QR.

Another thing that helps are good lock nuts on the axle that have decent knurling. The shimano ones like in this pic:

are OK but the knurling is shallow and the edges not sharp. I use old Campy locknuts that flare at the ends which has a larger diameter at the interface between the hub and the dropout.... it has more holding power. I also have had GREAT luck with old superbe pro locknuts that are REALLY grippy.

Cannot comment of FG, but for SS, there should be no reason you cannot use a QR