Besides the standard automax/bulleyes that the majority seems to use and recommend, my favorite, and certainly the best price wise, is the Wizard vibe probe.
Has adjusatable sensitivity, visual/audio/vibrate alert, very sentitive but to too much so, and even a little LED light for lighting up those dark holes.
They all tend to be slightly on the cheap side as far as construction from what I've seen, and they certainly are not made for aggresive probing.
I just picked up a new one after I busted my old one in a fit of anger after a year of hard service.
The only con I can think of is its gun like shape, which attracts curious and sometimes concerned looks from passersby at times.
The cheapest I found them, and where I got my latest one for $34.95 [US] is here
http://www.billsdetectorsales.com/pinpointers.html
I had an Automax Precision V4 for a while [got it for free with a new detector] , but I didn't even consider keeping it because of its huge size.