Within the subset of certified, normal category piston aircraft, you will find one of these two on a sizable proportion of those airplanes.

[1] https://en.wikipedia.org/wiki/Lycoming_O-360

[2] https://en.wikipedia.org/wiki/Continental_IO-550

To my knowledge some ultralights use regular unleaded (called MOGAS in some aviation contexts) and of course anything that you can buy an airline ticket for outside of perhaps Alaska will use jet fuel.

I mean in current production aircraft.

It appears that most versions of the O-360 can run on mogas, or unleaded gas of some sort.

https://www.lycoming.com/sites/default/files/SI1070AB%20Spec...

Indeed, there does appear to be a 100UL drop in out here too.

https://www.aopa.org/news-and-media/all-news/2021/july/27/ga...

I think at least all models of the Cirrus, one of the best selling general aviation planes right now, require 100 octane gas.

To be clear, none require leaded fuel, per se, but until this year there was no approved unleaded 100-octane fuel.

Turbocharged Lycontinentals, and higher-compression (9.5:1 or better iirc) stock Lycontinentals.