Red Trinkets
Red trinkets should do their job of rooting out deception that took no player skill,(Like cloaks and clones) that are completely due to the champ's kit.
That said, Red trinkets should show the alternate color of a clone that allies of the champion see. (Green Shaco, etc.) It's bad enough that these things can block perfectly aimed skillshots just with their bodies. But to be able to stop targeted things just because they exist is game-breaking. In before "But look at the movement and attack pattern." No. You can't do that when hesitation will get you killed by a crit from behind dealing 1000 damage with only 300 AD.