List some borderline-toxic gameplay effects you'd like to see in the future

Some gameplay effects out there could be really cool to have, but Riot shies away from them because they might be "toxic gameplay". Eventually, Riot's got to try them, or they're just shooting themselves in the foot.

Here's one example I have:

#Quedagh Curse Creates a large area (i.e. Trundle size) of Cursed Ground. Enemy Champions inside the Cursed Ground take modest true damage if they attack or use abilities. This Curse damage cannot be fatal.

Imagine being forced to fight in something like that. Ouch, huh? But the obvious counterplay is to walk out of the Cursed Ground, causing its effect to end immediately. That or some Champions with sufficient lifesteal or regen (i.e. Mundo) could just tough out the Curse damage. Add on that the Curse cannot kill you by itself, and it has its limitations.

In that vein, what sort of "borderline-toxic" gameplay would you like to see?