Personally, I use vi. But some people like nvu, and I've used Arachnophilia on occasion. Nice thing about Arachnophilia is that it's Java, and runs nicely under both *nix and Windows. Haven't tried MacOS yet, but it should be fine.

If I have to edit code locally on Windows, I'll use EditPad or TextPad. Under *nix if I want a GUI it's nedit.