so what's the weirdest intended or unintended (please clarify) interaction you've ever experienced in league. Is it gone or still available today? Leave your comments below.
mine was relic shield and shacos clone. Still available today.
I'm not sure about any item/ability interactions, but what about 
. Damage from thornmail heals you if you have gunblade.
Even if it's not a bug and it works as intended I simplay can't stand Ludens animation going of of 90% mages spell animations xD It's so awkward when it procs of Kata's bouncing blade or Xeraths Q xD
Zhonyas and any ability that can be channeled through it.
Like seriously.
applies 
's damage on his barrels.
and 
work aswell, but 
doesn't.
Also, Physical damage Sheen procs are the only on hit effects they apply.
It's not in the slightest buggy or even particularly bizarre by itself, but Cho'gath's e combined with Rylai's makes him the only champion I can think of with a manaless area-of-effect permaslow. Still in the game, intentional.
Kayle's e combined with Runaan's hurricane: Kayle's primary autoattack isn't a projectile but the Runaan's bolts are, which can lead to weird interactions with yasuo and Braum. Still in the game, intention status unknown since Kayle barely gets patched ever.
Not a champion-item interaction nor buggy but AP Cho'Gath with Stormraiders, since pretty much any ability hit on a squishy will proc it and mitigate one of his biggest weaknesses (kiting). Still in the game, intended.
There was the 5 censor 1 crucible Soraka build that cheesed the fact that at the time those passives weren't unique. No longer in game, it was intentional to an extent but as soon as it was realized to be super cheese it got removed.
