Vim for me.
I started out using notepad++ (hated it). Moved to JEdit (loved it; but there was so much missing that I could probably have written plugins for in Java, but didn't have the time). Moved from JEdit to Eclipse (I initially loved Eclipse, but over time I've started to really just... want to write code and not be hampered by annoying IDE stuff and the bloat and everything just got on my nerves).
The reason why I use vim is because of it's customisability. I was sat with a developer who used vim a long while back and was surprised at how many plugins they'd written themselves, and how easy it was to write a plugin too. Now I keep my vim folder under source control and have exactly the same vim wherever I go.
I also never have to use a mouse again! CLI + Vim =
