One of the most iconic trinkets in WoW is, I think, the Barov Servant Caller. It's a guardian trinket that you pick up from a questline in Scholomance. It's been around since Vanilla, pretty much unchanged other than the slight alteration during Cataclysm. It's fairly simple. Use it, and you get three guardians to run in and smack your target for you. Sadly, they don't actually cook or clean, despite the fact that the tooltip insists they do.
I've always viewed this trinket as a sort of rite of passage for all of my characters. Each one of them has this trinket in their banks. They don't really ever use the trinket, since it's practically useless after level 58, but they still have them tucked away in the bank. I'd like to see an update to the on-use some time in the future. I think if it's used out of combat, or if combat ends before the duration is up, they should shine your armor and cook a pig or turkey over a fire for you. Just because.