I love actually having the time and space to refactor a feature I wrote myself (something I'm doing right now for sn!)

Another things is implementing a design, it's nice to do some fronted work where there's no ambiguity or decisions to be made on my part how things look just need to make it look like the design.

Igniting the spark in other developers and seeing how it changes their code and/or their process (shortcuts etc.).

Refactoring!