Smultron is an open-source text editor written in Cocoa for Mac OS X Panther with many of the features that you might need. It features easy selection of the opened documents, line numbers, support for syntax colouring for many different languages, support for text encodings, code snippets, a toolbar, a status bar, HTML preview, multi-document find and replace with regular expressions, possibility to show invisible characters, authenticated saves, command-line utility, .Mac synchronisation of preferences and many more features.
Pros: Smultron is fast, open source, and supports customizable syntax coloring.
Cons: None significant.
Update: Smultron was discontinued by its original developer. The source code was recently given to a new developer, who is now developing it under the name Fraise.
[…] Fraise is a direct fork from a previous Favored Freeware title, the now-discontinued Smultron. It is lighter and faster than most other text editors, open source, offers customizable syntax […]