A few come to mind. I use the Tejon. Very light, deep and easy to use once you get the hang of ground balancing it. There are tons of coils for it to fit just about any situation you come across. It doesn't have a lot of whiz bangs, but it gets the job done, has a lifetime warranty, and doesn't cost an arm and a leg. It is a great machine if you don't need doodads telling you what to dig.
The Nautilus. Very deep machine with the monsterous coil they have for it. Multi-tone, but can have a steep learning curve to use if effectively. Cumbersome if you don't mod it to make it more ergonomic. More expensive than the Tejon, but deeper with that big coil from what I have seen.
F75 or T2. Very nice machines with lots of whiz bangs. I want a T2 myself, but haven't convinced myself I want to learn a new machine all over again. I don't even know if they make any other coil besides the standard coil for them yet, but they both get great reviews. The T2 did very well is the nastiest soil I had ever come across, better than my Tejon, or at least the signals were more readable as good signals. My Tejon saw the targets, but the signals weren't something I would normally dig. Knowing the area, I would dig these signals anyway and find relics and not the junk they sounded like. The F75 is pretty expensive. Both of these machines are very light as well.