I’ve been a loyal user of TextMate for many years – it’s my go-to editor for the majority of file editing, source code and otherwise. Going back a number of years, you can read a few tips I wrote about TextMate (this content is dated):
Approaching six years in the works, lead developer of TextMate, Allan Odgaard, has decided to open source the code for the 2.0 version. Important point, Allan has not abandoned TextMate, far from it – please take a minute to read Allan’s post about his decision to go open source.
TextMate Source Code