Hazel Lee does a few tricks for us here, including the standard "doacircle" trick. She'll actually "doacircle" in both directions, but didn't feel like going "otherway" this particular day.
I didn't get around to teaching my last guinea pig, Acorn, any tricks early enough for her to be at all interesting in that aspect, (she was in every other, so it's all good) but she could "doacircle" and we would pass a little wooden cylinder back and forth every so often. Our favorite game was blocks; I would hand Acorn a block, and if she approved of it, she would take it from my hand and drop it. It was more fun than it sounds, trust me XD
Hazel Lee is proving to be a smart cookie, though; despite her general dislike of being outside of her cage, petted, or cuddled, it looks like we could become good friends through training :)