What's the most unexpectedly fun/strong strategy you've played?

As the title asks. For me it is definitely AP Nasus mid lane running arcane comet and domination. E max first, building into . Your E hits so hard you can constantly poke your opponent for large chunks of their hp whenever they get close to last hit minions. It also gives you such powerful waveclear that it forces your opponent to cs under tower. Only downsides are you're not as tanky and you don't get to stack your Q until later.