Lissandra and Taric
This has been bugging me since his rework, since the very fact he got a visual update after Lissandra's release means there is no excuse whatsoever for this:
Bloodstone Lissandra is the right color. The gem is a grayish green with red specks that look like splattered blood. Hence the name.
Bloodstone Taric, THE GEM-THEMED CHAMPION, is the WRONG GEM. It's either ruby or spinel, but certainly by no definition is it bloodstone.
And you might think, well it's totally red and he looks like a vampire so maybe that's the reason it's called Bloodstone. But the problem with that reasoning is that it would only make more sense for it to be actual bloodstone, if that were the case. Bloodstone has links to blood and magic that ruby does not.