The short answer is "the one you use". Chris suggested some great resources. Look up contact information for a local orienteering group to get more experience. It's a lot of fun and can be good exercise too!

I use a Silva Ranger compass almost every day in my profession (no, I don't get lost all the time <img src="images/graemlins/smile.gif" alt="" />). Suunto make one almost identical. The important feature for me is the ability to set the declination. This is important when locating land boundaries or performing simple mapping measurements. It also has a built in clinometer (or "inclinometer") which can be used to measure slope gradient.

I like the "sighting" type compasses the best. They have a mirror on a hinged lid which enables you to sight through a notch over the compass while looking into the mirror and aligning the north arrow. I've always thought the mirror would make a good signalling device as well. I know it helps when you get something in your eye. If I recall correctly, Silva makes one called the Guide which runs about $15. While you cannot set the declination it does have a declination scale which allows you to easily account for it.

Remember to bring a map with you too. If you're lost you can usually figure out a bearing to follow to get you to a road or stream. Trust your compass. Lots of stories are out there about people who had a compass but didn't trust what it told them. That needle is going to point to magnetic north unless you're standing on one of the poles. I'm not so sure about a GPS unit, however (and I teach folks how to use them as part of my job!). Electronics and batteries fail, coordinate systems can be tricky, and most of us refuse to read instructions anyway. Even if you carry a GPS unit I encourage you to carry a map and compass (and know how to use them). I'm a map nerd anyway. When the weather's bad outside I curl up with a good map and dream of where I want to go next.

Terry