I'm with everyone else who recommended the Tek Delta 4000. I have one and I absolutely love it. It's simple, hits very DEEP, weighs almost nothing, runs on only ONE 9v battery and has the best and easiest pinpoint feature you could ever want.
I took mine to most of my "hunted out" spots when I first got it and found MANY targets and treasures my other machines completely missed, including two gold rings and two silver rings. It also sniffs out really TINY targets time after time. Frankly, I was amazed at the time. Now I just know to expect great performance.
In that price range you just can't beat it.