A common complaint I’ve heard from my colleagues is that their favourite and best work is their least appreciated and least cited work. (I certainly feel this way.) It is not hard to imagine why this is: probably their best work is the one that contains the most unfamiliar and original ideas, the most difficult calculations, and is probably the least clear to anyone except the author because it is very difficult to explain something truly new.
(This all rather puts me in mind of the quote:
Don’t worry about people stealing an idea. If it’s original, you will have to ram it down their throats.
Howard H. Aiken, as quoted in Portraits in Silicon (1987) by Robert Slater
So, if you are looking for something truly interesting to work on why not pick an author you respect and find their oldest least cited paper. (I.e., don’t choose a new one that simply hasn’t been read yet.) Read it forwards and backwards until you completely understand it.
There will surely be some treasure buried in there.
And hey, you can be pretty sure that absolutely noone else will be working on the same thing.
(My personal pick is the intriguing paper of Bill Wootters on entanglement and parallel transport.)