Here's our list of compasses that offer basic functionality with everything you need -- no bells and whistles (actually, one does have a whistle). All have excellent reputations and are good quality at a reasonable price. You can spend more to get more features. You can spend less for a simple zipper-pull style compass that stays attached to your pack (but should be considered a backup compass, not a primary).

All recommended compasses have a rotating bezel (ring) marked in degrees, and the non-moving baseplate is marked with 360 degrees. The magnetic arrow points to magnetic north. Note that a fluid-filled varieties will allow the needle to settle to its position faster than a non-fluid type. I consider adjustable declination a necessity -- the magnetic variable between where the compass needle points and True North.

Each recommended compass has this feature, as well as a ruler. You want one with a ruler in inches/mm because it's helpful for measuring distances on a map. A 1:24,000 scale is handy for use with standard USGS topo maps. All baseplates have an orientation bearing line down the middle to indicate the heading orientation (where the compass is pointing in relation to the north arrow).

A compass should always be part of the gear you pack and is a necessity when navigating from a map.