It might not be a small task, but NPC's in games could be interesting and might be very popular. At least for the first few games.
But also the help function in almost all programs could benefit of my help.
And the obvious ones are of course a virtual friend as well as chatbots in all kind of fora, both about specific subjects and the more general ones.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence