Favorite legacy lens to use on Micro 43?

The Zeiss 35mm 1.4 works very well with m43 (at least a G2 and OM-D - see my other answer), but is expensive, big and heavy.

The Nikon has many fans. I had it once, but didn't like its rendering & got rid of it. No idea how it interfaces with a sensor.

There are certainly others as well, but fast shorter FF lenses often do cause interface problems and buying one just for that use probably isn't worth it (I keep & use mine to shoot B&W film).