For big jobs, I use SlickEdit. Otherwise, it depends on where I'm at and what my mood is. If I'm at a terminal window, I'm likely to use emacs. If not, I'll pop open TextMate. I write a lot of LaTeX in TextMate. Recently, I've been using vim a lot too. I'm finding I like modal editing of vim over the multi-key combinations of emacs. Plus, no emacs pinky! I really couldn't get used to vim's default cursor keys (h, j, k, l), so I mapped instead an inverted T on i, j, k, l.