MTG Combo: Devoted Druid + One with the Stars
Infinite mana combo. One with the Stars makes Devoted Druid an enchantment and no longer a creature, meaning it has no power or toughness to be affected by -1/-1 counters. Note that being a creature is not a requirement for having counters put on it, so an infinite amount of -1/-1 counters can be put on Devoted Druid for as long as One with the Stars remains attached to it, and it wouldn't die.