The Tesoro Compadre[0] is pretty great and very affordable.

Best in higher end might be Nokta[1] and its sister company Makro[2].

Anything from any of those three companies will be good and high value.

[0]http://www.tesoro.com/product/detectors/compadre/index.html

[1]http://noktadetectors.com/

[2]http://makrodetector.com/