In the past, I have used the Garmin GPSmap76 and GPSmap76S. These are older models, no longer produced, but tough as nails, and quite accurate. You can probably pick one up on feebay quite reasonable. I have actually owned seven of these units, and still have three, all which were used extensively for geocaching.
As mentioned before, there are places that you might not get clear reception/coverage, due to rugged terrain, and/or dense overhead foliage. Generally, you can work around these conditions. Also remember, for a gps to function accurately, you must be moving, so it can calculate your position, and direct you towards your desired coordinates. A gps is a smart tool you say, but actually, a gps only knows two things: the gps knows where it is now, and it knows where it has been, therefore it knows what direction it is headed. Everything else is calculated, based on those two things, along with your input...(where you want to go).
Good Luck & Happy Hunting !
