The one I use the most, and which I find the most versatile, is a Sceery AP-6 Variable Predator call. Very easy to use without the freeze-up problems that plague the closed reed calls in cold weather, and more forgiving than an open reed call. With a bit of practice, you can also turn that thing into a very decent cow elk call.
My other go-to call is a Sceery double reed / double barrel open reed call. Huge volume on that thing (makes my ears ring), so it needs to be used in the right conditions or not at all. But it's been an invaluable tool for bringing 'yotes in from great distances. Haven't seen it for sale anywhere lately, so I'm not sure if they make it anymore.
In the end, though, I've called in coyotes with all kinds of mouth-blown calls. Any decent call is going to do the job -- and I'm quite convinced that 90% of anyone's success comes from the set-up, not the sound. A great many coyotes respond to a call but are never seen due to poor visibility on the approach, or spotting / scenting the hunter. The call you choose to use is, truly, not that important compared to the other details.
My 2 cents...