We use Wellness Wellbites mainly. They're great since they're soft and you can break them up into teeny tiny pieces. Other than that, little pieces of cheese, apple (w/o the skin), and kibble from his leftover bag of Canidae that he refused to eat when it was in his bowl, but will when I feed it as a treat *shrug*
Yes Mochi loves these... They are small and perfect size she does get tired of the same variety all the time i use all kinda of treats. When we did training classes we had like different level of treats so string cheese and thing fishy would be Mochi's highest level of treats while the zukes and others would be lower level ones.
Oh man, I seriously have like 4 different kinds of treats for Theo. I use the wellness treats as well. Those I use for our walks and general training. Theo loves them and they're really easy to break apart so I can control how big or small of a treat I'm giving him. At night when I put him to bed in his crate he gets these soft peanut butter treats...they're called Buddy Bites I think? He always goes running and jumps in his crate when he sees me open the bag. In the morning when I put him in his crate while I get ready, or if I leave him in his pen to go somewhere, I give him these crunchy lamb rounds from Natural Balance. He loves those too. I also give him dried sweet potatoes when I'm leaving him at home for an extended period. It's like a rawhide replacement, but also just kind of a treat that takes him awhile to eat.
I don't know what stores you have in your area, but there's a store called Pet People in my city that sells them, and another store called Kahoots. I've also seen them in a couple of others. I don't think places like Petco or Petsmart sells them, but any "upscale" pet store will have them. And by upscale, I just mean like the equivalent of whole foods where Petco is a big chain grocery store.
For store-bought treats, I use Zuke's Mini Naturals and Charlee Bear training treats. When I'm short of cash, I take a turkey hot dog, dice it into tiny cubes, cook them to a crisp in the microwave, and dab them off with a paper towel. Any leftover pieces get frozen so they stay good.