All-Star Akali

I have Snow Bunny Nid and Kitty Kat among others from around that era (including Red Card Kat as well).

Ice Toboggan Corki

Nosferatu Vladimir, Definetely Not Blitzcrank, Kingpin Twitch(I've never seen someone else use it, just myself), Franken Tibbers Annie,
Mr. Mundoverse, Scuba Gragas, Firefighter Tristana, Dragon Knight Mordekaiser

and some other skins that arent available anymore

but I wish I had some of the very early skins

PAX Sivir. I think that's my rarest. I'll have to dig through my skins

Victorious Jarvan.

I have many legacy, limited time, and some unpopular skins, but I'm pretty sure that's my rarest. Oh wait, except maybe Crimson Akali. For whatever reason everyone else prefers the ugly ass Stinger...

Judgement Kayle

Urf the Manatee Warwick, Workshop Nunu and King Rammus