My most often used compass is my watch, a standard mechanical military issue Marathon GSAR, only works in the daytime and being in Australia, I usually have the Sun handy (hey you didn't specify only magnetic compasses) it is accurate to within 5 degrees. When it is cloudy I use my Brunton Pocket Transit, the best little big compass that I know. Yes, I agree that it is a little heavy, so it stays in the car and is used for general purposes while travelling. My favorite is a Silva Sightmaster compass, I had to leave mine in the states when I returned to OZ as the balance was all wrong for the southern hemisphere.

My backup in my PSK is the NATO survival escape and evasion button compass, not that accurate, it consistently points about 20 degrees of north, I think it was shipped too close to a magnet I have yet to tear it apart and remagnetize it. It is slightly better than looking for lichen on trees.