You will get a ton of different suggestions.... it really depends what you want to do with it, and your ground conditions. Assuming you want to find coins, the three mentioned are good choices.
Fisher F2 - versatile entry level metal detector
If you look at the F2 be sure to check out the package with the second 4" a coil and pinpointer for only $16 more than the machine by itself.
Teknetics Eurotek Pro
The Eurotek Pro is super fast, and has adjustable iron audio - a feature usually found in md-range detectors.
Garrett Ace 350
The Ace 350 has the advantage of a DD coil, which are usually found standard on most mid-high end detectors.
Here is another choice:
Tesoro Silver uMax
They are lightweight, have a silent search all metal mode, and are 100% audio response (no display)... backked by a lifetime warranty. Don't let its simplicity and size fool you!
Hope that helps!