Harrison's is the best hands down.
However, I will throw a little testimony in here for one that isn't mentioned and that is Primos Hoot Flute
This weekend, I went out and got the owls all fired up with that thing.
I had them come in a light over my head, cackling and everything. It isn't loud but I can get the local owls fired up and if there is a gobbler within a mile he is going to have to tell off where he is.
