List of available skins in Agar.io (updated as more are added)
To apply the skin, change your name to any one of these:

Alphabetical order:
2ch.hk, 4chan, 8, 8ch, 9gag, argentina, australia, austria, ayy lmao, bait, bangladesh, belarus, belgium, bosnia, botswana, brazil, bulgaria, byzantium, cambodia, canada, chile, china, cia, confederate, croatia, denmark, doge, ea, earth, estonia, european union, facepunch, feminism, finland, france, french kingdom, german empire, germany, greece, hitler, hong kong, hungary, imperial japan, india, indiana, indonesia, iran, iraq, ireland, italy, jamaica, japan, kc, latvia, lithuania, luxembourg, maldivas, mars, matriarchy, mexico, moon, nasa, nazi*, netherlands, nigeria, north korea, norway, origin, pakistan, patriarchy, peru, piccolo, pokerface, poland, portugal, prodota, prussia, qing dynasty, quebec, reddit, romania, russia, sanik, satanist, scotland, sealand, sir, somalia, south korea, spain, stalin, steam, stussy, sweden, switzerland, taiwan, texas, thailand, tsarist russia, tumblr, turkey, ukraine, united kingdom, usa, ussr, vinesauce, wojak, yaranaika

Order in which skins were added:
poland, usa, china, russia, canada, australia, spain, brazil, germany, ukraine, france, sweden, hitler, north korea, south korea, teta delicia, united kingdom, earth, greece, latvia, lithuania, estonia, finland, norway, cia, maldivas, austria, nigeria, reddit, yaranaika, confederate, 9gag, indiana, 4chan, italy, ussr, bulgaria, tumblr, 2ch.hk, hong kong, portugal, jamaica, german empire, mexico, sanik, switzerland, croatia, chile, indonesia, bangladesh, thailand, iran, iraq, peru, moon, botswana, bosnia, netherlands, european union, taiwan, pakistan, hungary, satanist, qing dynasty, nazi*, matriarchy, patriarchy, feminism, ireland, texas, facepunch, prodota, cambodia, steam, piccolo, ea, india, kc, denmark, quebec, ayy lmao, sealand, bait, tsarist russia, origin, vinesauce, stalin, belgium, luxembourg, stussy, prussia, 8ch, argentina, scotland, sir, romania, belarus, wojak, doge, nasa, byzantium, imperial japan, french kingdom, somalia, turkey, mars, pokerface, 8

*Nazi skin will NOT be displayed in the following countries: Germany, Italy, Poland, Hungary, Brazil, Austria