I love trick training and my horse has just the right character to enjoy it, too. For now he knows carrying an object (a crop, usually), marching, climbing on different objects with his front legs or all four, lying down on his side, on his chest (this includes also letting me mount him and then rising), sitting, rearing (from ground only), backing up from tail, and I'm working on bowing and hugging. These activities really lighten up the daily groundwork. :)
Other tricks sound neat, too. I'd like to teach him kissing, saying yes and no, and I've got ideas for others building up.
I have come a long way, to surrender my shadow to the shadow of my horse.