I have a somewhat unlimited supply of Master Balls because I play through my GBA games so often. I've used four so far, all on Pokémon I just didn't have the patience to dwindle down to 1 HP and a status condition. Those Pokémon were Mesprit, Cresselia, Heatran, and, just a few minutes ago, Giratina. I tried Dusk Balls at first but I only had 3 with me, so after a couple Ultra Balls I decided it would be easier to just throw the Master Ball.