MacVim

If you're a vi fan AND a Mac user, Macvim (the code.google.com hosted version) is a must -- much better integrated with Mac's overall interface than Apple-distributed vim (constrained to only run in a Terminal.App, and otherwise very interface-constrained).

Well, it's Vim. Natively on a Mac. Nuff said.

MacVim is the best Vim implementation for Mac OS X I've been able to find. I've been a Vim user for ages, so this is _perfect_ for me :)

It has a pretty steep learning curve, but once you get a hang of it you can't live without it anymore. As a Ruby on Rails developer I've tried several different editors/IDE's (including TextMate, Aptana, Netbeans, RubyMine, etc.), but I keep returning to MacVim because of it's handy scripts/shortcuts/infinite amout of customizations.

Bliss.

MacVim is what you should be using if you're a programmer under OS X. It's integrated nicely, you can launch it from your shell prompt, it's nimble, customizable through your vimrc as well as some GUI preferences, and development is active.

On the user+developer mailing list at http://groups.google.com/group/vim_mac you can keep track of what's happening.

With a nice theme (I made my own) and good-looking font like Inconsolata or Monaco, it fits right into that vain OS X feel. :)

Vim itself, whether in a terminal or GUI, is the best tool I've found across any OS, for any hacking, but especially web development (Ruby on Rails - I recommend the rails.vim and fuzzyfinder.vim plugins, the latter recently extended by Jamis Buck to make the searching smarter).

You have to spend some time learning commands and customizing it to your liking, but that investment will pay back massively.

Great Vim for OSX...