Bug: Scheming Fence & Halo Fountain
In a game in Historic Play, Best of 1, I played Scheming Fence and targeted the opponent's Halo Fountain with his ability. I then put a Security Bypass and Goldvein Pick on the Scheming Fence and attacked with it. While it was tapped it let me use the Halo Fountain's first activated ability "W, T, Untap a tapped creature you control: Create a 1/1 green and white Citizen creature token." twice, while targeting the Scheming Fence itself to untap. (the Scheming Fence was already tapped from attacking, and shouldn't be able to tap to pay the activated ability cost. Targeting himself to untap does not untap him, however you can use the ability infinitely or for however much mana you have. I tried it to see what would happen, because it lit up as something I could activate, then activated it a second time just to see if I could, and then stopped as I didn't want to abuse a bug. It had no impact on that particular match, but should be fixed)