Roxie wasn't very tug motivated when I first started her, but I got her turned on with a tug pouch that has a pocket that you can put food in. I would put her cheese in it and then throw the pouch(or tug) and when she brought it back to me I would open the pocket and reward. Tugaway Tuff Pouch Tug Toy
Roxie is also ball obsessed. I got her the Chuck it Ultra Tug but I tend to find that she looses her mind if I use it. I think I even created the problem of her pulling out of her weaves early to chase the ball last time I used it. But its one that if I need her undenying focus, that will get it. Chuckit Ultra Tug
Mostly I just use food. Main agility treat is sting cheese. It's easy to throw in a pocket and I am ok with having to bite off chunks with my mouth.
For trials and such I use those dog food rolls you can find at a pet store, or liver. Something high drive and smelly that I can rub all over my hands before we enter the ring.