...The look on their face when you give them a brand new chew, a type they've never had before.
I gave Harley a lamb ear today and he sat by it, smelled it, licked it, looked at me, jumped around a bit, licked it, looked at me, repeat... tried to pick it up, licked, look, repeat... he was soooo confused. About 15 minutes later I think the lightbulb turned on, and there was no way I was getting that from him. lol
Totally made my day.