Thinking of "gig economy" jobs, there's some that stick out to me.
- Nurses. You could take on assignments to visit Elders in their homes and socialise with them, give them health checkups. If you had Get to Work, there could even be a gig to visit the hospital and do a shift there for a day like an Agency Nurse.
- Entertainers. This would be the PERFECT way to introduce bands. You visit bars and residential lots hosting parties, and either play instruments (hopefully with a "Play Together" interaction to actually function as a band), you could tell jokes as a comedian to an audience that booked you ("corporate" gigs as standups call them), or even borrow some of the Tragic Clown animations and do things like make balloon animals and juggle, like at a children's birthday party.
- Maids. Simply put, you take on gigs at a Home Cleaning Agency to clean up random lots. Pretty simple, really.
- Escorts. This is one the mod makers will have to make, but it'd be "gigs" that are in fact types of Sim. So you get a gig to go on a date with a Geek Sim, a Bro Sim, a Romantic Sim, an Elder Sim, etc etc, and you get paid accordingly. Again, not expecting Maxis to make this one, but it could totally work as a mod.