Golden Gauntlets, Pegasus Boots, or Farore's wind, I could get to Vermont to go snowboarding instantly instead of driving there for 5 hours
Super strength and speed are too tempting, I would've said double clawshot, but when I think about what they could actually grab onto and how often I would feel like going around tearing up city buildings and annoying the hell out of people because of it, I don't think I'd end up using them that often
Actually, maybe the Ocarina for time travel, going back in time to be trained by real samurais or ninjas = awesome, plus I procrastinate so slowing down time to do my homework would help too lol