Twitch and Eve used to have real stealth that lasted 50 seconds. *Fifty*.
There used to be a summoner spell that caused *every single turret on your team* to become immune to damage, deal 50% extra damage, and deal aoe splash damage on attacks. It was usable while dead, had a low cooldown, and granted kills if the shielded turret killed a champion.
It was rarely taken as it was considered to be revive-tier.
Anivia used to be able to egg teleport. If you started casting teleport before you egged, the channel would continue into egg form, allowing you to teleport to safety. And it actually worked because everyone and their goddamn mother didn't have a hard CC back then.
There was a time when Janna was an ADC.
(And be creative, don't post pleb tier shit like "TF and Xin Zhao used to be OP gyuh gyuh how weird huh guys")