Let's Be Dinosaurs!
A LARP made by a child! About being dinosaurs! Technically it is a LARP and not an RPG but I think it can be played at the table like an RPG. Only requires printing out the 2 page PDF ( http://www.goldencobra.org/pdf/2016/Let%27sBeDinosaurs!_Beltran.pdf ) passing it around the table and reading it, and writing down the traits of your dinosaur on an index card.
Not sure if you wanted a one shot. I suppose Let's Be Dinosaurs really only has replay value if you're very interested in dinos.