Mouth calls: cottontail and jackrabbit distress calls, Dan Thompson Red Dessert Howler, lip squeaks. You shoot way more than I do, so I don't know that I really have anything helpful to offer! I think the Mojo Critter or other, similar decoy would be a good addition to my pack- might get the prey drive to kick in a little more. The howler I mentioned may be doing more bad than good. Some guys use them as locators before daylight, then go back to the spots where they got answers and hunt them with regular calls during the day. On the other hand, I've seen videos of coyotes and bobcats coming in to just the howler (in other states).
One idea I had would be to use pre-recorded soundfiles on my cell phone- you know, call 'em in with the real thing. So if I want to call foxes, I might use this: http://www.youtube.com/watch?v=jofNR_WkoCE
If you guys have any links to sounds that might work, post 'em up!