I remember playing a character with disassociative personality disorder for months in a roleplay. One of the other players finally realized it and their response? ".... she has multiple personalities? That explains so much."
Was a point of pride for me that they didn't figure it out right away, and it explained what people thought where holes and inconsistencies when they did figure it out. I never once wrote IC that they had the disorder
I would lead that on back to the OP's original question and offer my advise in the form of 'any idea can work, if done right and in the appropriate time/place'. Everything that's considered overdone/cliche can work if given a new spin. If you take a cliche idea and run with it 'just because I can' and it makes no sense to the story or context that the character is being played in, then you run into problems (IE the aforementioned assassin characters that tend to not make any sense, or sit around in bars asking people to hire them to kill someone). Another failing is to take cliche ideas because they're easy. IE, dead parents so you don't need to worry about writing for them, but they have no actual impact, depth, or bearing on the story. This tends to feel like a cop out and doesn't illicit any sort of emotion from readers other than maybe exasperation.
However if you take an overly abused idea (IE multiple personalities, vampires, dead parents, etc) and make it your own. Give it depth and meaning, and make it make sense for the overarching story? Then there's nothing wrong with a cliche.
I have a character with a dead mother. Mother passed away due to natural causes. The death of the mother is in there specifically to facilitate and explain the strong the bond between the character and her father. The mother isn't just some name on a sheet to forget about. The father is known to reminisce about the mother during periods of nostalgia and the mother is as much a character as the living ones. To me this is a fine way to implement a sometimes overdone concept (dead parents) for a story purpose. It's not just a 'what can you tell me a bout your characters parents' being met with 'oh, they're dead so I don't need to think anything up'.