I really prefer the ones that require a hike, biking 
or climbing or whatever.

However, I also enjoy doing the ones that involve some mental challenge.
Many of the urban caches have clever hiding places, riddles, difficult
to get to locations or clues that require some thought.  I like to do 1
or 2 of these when there isn't enough time to for a longer trip or big
adventure.

Frobro D-Dubs