Skins

You should be able to get these skins (if you own all the skins) through Mystery Gifting yourself or others Mystery Gifting you:

List of Skins which are not obtainable according to the source:

Achievement Skins

Victorious Skins (obtained by reaching Gold or higher in a Ranked season)

Victorious Jarvan IV (Season 1) Victorious Janna (Season 2) Victorious Elise (Season 3)

Refer-A-Friend (RAF)

Grey Warwick (refer 25 friends who reach level 10 or higher) Medieval Twitch (refer 50 friends who reach level 10 or higher)

Other

Triumphant Ryze (win an official League of Legends tournament) Riot Girl Tristana (become a fan on the official League of Legends Facebook page) Unchained Alistar (subscribe to the officialLeague of Legends YouTube channel) King Rammus (awarded to players who participated in Closed Beta) Judgement Kayle (awarded to players who played at least 10 matchmade games in Season 1) UFO Corki (awarded to players for voting in the Reader's Choice Awards 2009)

Collector Edition Skins

Goth Annie (Digital Collector's Edition) Black Alistar (Digital Collector's Edition - Preorder) Silver Kayle (Retail Collector's Edition) Human Ryze (Retail Collector's Edition - Preorder)

PAX Skins

PAX Twisted Fate (PAX 2009) PAX Jax (PAX East/Prime 2010 & PAX East 2011) PAX Sivir (PAX Prime 2011)

Others Mentioned

Rusty Blitzcrank Urf the Manatee Championship Riven Riot Squad Singed