Items that are no longer available

Just what the tittle says, id like to know if there were some exclusive event items that I won’t be able to get (if so I want to know how good those items were) In case that they are not obtenible anymore, it’ll be good if anybody tell me if I’ll be capable of get the best items/gems/costumes/whatever in the game even without those “event/limited items”

Duplicated topic: Items/heros that are no longer available?