When working on an emulator, a feature never really feels finished. Last month, crudelios triumphed with his new software bounding box implementation. It was easily the most accurate implementation of the feature to date. A few months before that, magumagu created more accurate disc timings to make games load more accurately. RachelBryk has been steadily adding features for TASing for years. Perhaps a longer term, more general project is Sonicadvance1's continued work on Dolphin's ARM port which is always receiving updates.
All of those features have seen further refinements and work this month that enhances their usability! Sometimes these changes are from one author continuing their work, but a lot of the time other contributors will join in with their own ideas, fixes, and add-ons. Just because a feature exists in the emulator doesn't mean it can't be improved further!