I use 2 different ones, the widowmaker(not made anymore-produces all sounds from bleat to big buck grunt) and the Kn' H Ez Grunter Plus(which allows you to inhale and exhale to produce different tones and the hypervent sounds of a buck-no oring so non adjustable).

The true talker is the most popular as it allows you to mimic all sounds without changing a oring on the reed, but it is also the biggest and most bulky! Still a good call with good tone, if you want the extra sounds it can produce. If your looking for just a grunt the ez grunter is a good one and I have yet to have it freeze up, the main reason why I use it!