Pineapples
The grass is always greener, and other people always do much cooler research. I suppose in practice it must often turn out to be a long slog like anything else, but I do envy anyone who can devote their time to a single field of study and then turn the whole thing into a book which non-specialists will actually read. The example I found today is Fran Beauman's The Pineapple, reviewed in the TLS. A book entirely about pineapples - how wonderful is that?