User blog comment:KaiserLos24/Skins- Symbolism or Just For Show?/@comment-24337098-20131230111110

I'm still working on improving my Kha'Zix, but I can guarantee that my win rate got a bit higher after I bought Mecha Kha'Zix (because it shows the isolated targets excelent + the sound of finding an isolated champion is very easy to distinguish)

I also heard ocelote (yeah, I watch a lot of streams) talking about the Clockwork Orianna skin, saying that he manages to see his champ better in teamfights using that skin.

My personal opinion about skins is: You should get a skin for a champ regardless of your knowledge about that champion if that skin brings any kind of extra-utility.

The skins which I find useful are:

Mecha Kha'Zix (reasons stated above)

Justicar Syndra (the arrows that show the direction of a ball if E is casted are yellow instead of blindish purple)

Arcade Sona (nice info about the power chord effect, useful in close-call situations)

Underworld Twisted Fate (I think that the cards from Q are a bit harder to dodge, because the model is smaller, but the area of effect is the same)

Arclight Varus (it's easier to see when the Q has reached maximum cast range)

Sad Robot Amumu (accurate range info of W, on classic I feel that the range is a bit larger)

I can't find other skins that really can give some good utility.