I'm looking for a word that can substitute an object, whose name is unknown to the speaker.
I'm aware that there are words like "whatsamacallit", "thingamabob", etc., but they seem to be colloquial and I have never heard/seen any such word used in a formal setting. Is any of these common placeholder words appropriate in any situation?
For example, let's say I want to compliment a stranger, but I don't know the English word that represents the object I'm talking about: "You have a nice [placeholder]". What should the placeholder be?