It seems there is one in every game, lol. I had a scientist in one game that only wanted to push the boulder....24/7. I had to keep putting her back to work and babysit her the whole time.
Another game, it was the builder. Another the farmer.
I have been letting them try everything once, see how much they gain on the bars and whichever gains the most, that is what I let them do. (if i don't notice one gained more than the others, then I let them do something fun or non work related, like push the boulder or swim if far enough along, then see where they go on their own. Noticed they work better if THEY choose what they do. If I see someone likes rough wood but they won't build, I stick them on beach clean up and they whip it clean quickly, lol.