Textmate has to be the most amazing text editor I've ever used. In the past I've used BBEdit (on Macs) and UltraEdit (on PCs) but this is by far the best. What makes it cool is that much of the functionality is present in "bundles", which can be removed and added at will, to integrate it or use it with almost any tool, language or environment (at the moment there are 128 bundles).
Now I still love Intellij as my primary Java tool on any platform but for all other text editing needs I use Textmate. It even won Best OSX Developer Tool at the recent WWDC.