depending on your budget, there are a ton of choices out there...
under 300 bucks: garrett ace 250..good detector, cant stand the bing bong sound.
fisher f2: very fast recovery, good separation of targets pretty accurate vdi of targets.
under 200 bucks:
Tesoro Compadre. On the forum I'm at all the time, this machine beats out everything. Some people have even sold their eTrac and use this. it's a simple learning curve and it's hot on gold.
400-600 range:
Some ppl will say Minelab 705...you can switch frequencies so you can have a better option for silver/gold etc...the downside is you have to change coils for these different frequencies. that gets expensive.
Tesoro Vaquero: great ground balance, great pinpointing, great in mineralized soil and lifetime warranty. Light, weighs 2lbs. Again, there are people getting rid of their 1400$ machine for this one. It's good on relics, coins, jewelry and bad mineralization in the ground. oh..and deep....there are people who have found coins at almost 17".
Fisher F70: great machine. deep as can be. awesome on relics/coins/jewelry. It's pretty light too. 5yr warranty i believe. Horrid in high mineralization. I was looking at this for an upgrade but after a ton of research and speaking to some dealers, they all say it's way too sensitive to be used in high mineralization areas. Also very sensitive to EMI. My F2 is horrid in some places. Can barely get above 1-2bars of sensitivity.
Tesoro Tejon: most ppl use this as a relic hunter. It's very very deep. Great separation of targets and great discrimination.
from 600-1500:
Fisher F75LTD: same as the F75, but has a backlit screen and goes a bit deeper. Otherwise, pretty much the same. ppl use this quite a bit for relics because it has a boost mode for going deeper and it does.
Pretty much the rest of the Tesoro line. Some for water only, some really used by hardcore relic hunters.
Minelab eTrac/safari/explorer etc... great machines. pretty expensive. Short warranty. Super deep and they kill on silver. slow recovery and target separation. have to swing these slow. Huge learning curve to these. Can plug the eTrac into your computer and download/create programs for different situations.
White's detectors are all solid machines. The newer stuff they're coming out with the v3's and such are phenomenal machines. I just don't have any experience at all with them, so didn't write anything about them. People are very loyal to White's though.
I've been doing a ton of research and I'm getting a Vaquero. Besides the normal parks and such around here, our hunting camp (which was grandma's farm until she moved into town) is huge, dates to the mid 1800's and I have hundreds of acres of woods and Lake Superior lakeshore to hunt. Vaquero is one of the best all around machines. One more thing: Tesoro machines hold their value very well. So if you decide to sell it, you can get a good % of your money back.
One more good thing: only uses 1 9v battery. Lasts 15-20hrs with headphones on.
Also...Kellyco is great. But they won't give you crap for a deal. If you get on the friendly metal detecting forum, pm me IMshooter, and I can hook you up with a dealer that'll give you a heck of a deal. Usually a great price and a propointer (best pp on the market) or a Lesch digger.