TextMate has an extensive library of plugins which can be further extended to make it even more powerful.
Ranked in these QuestionsQuestion Ranking
Pro Open source
Textmate is open source and hosted on GitHub.
Pro Lightweight footprint
It's lightweight footprint makes it extremely fast to load and use.
Pro Multi line select and editing
Pro OS X only (native)
Pro Built-in access to MDN
Chocolat offers integrated web-based documentation, so you can quickly look up anything you might need clarification on.
Pro Unlimited split viewing
Chocolat allows you to view as many files side-by-side as you'd like, rather than limiting you to two.
Pro Live error checking
Chocolat supports live error checking.
Pro Great look
The native Mac looks awesome.
Pro Excellent theme support
Themes can be tweaked in various ways, such as in terms of font-size, colors, and highlighting colors.
Pro Code completion
Chocolat will auto-complete JS variables, keywords, methods, functions, and parameters.
Con OS X only
TextMate is for OSX only.
Con Mac only
Chocolate is only available for Mac.