This is a zombie, I suppose, but I’m new here and I love text editors. It’s a shame not to have a real one; I’m not sure how people get by with notepad and the like for so long.
I’m on a Mac. There are a few well-regarded ones:
TextMate, which I use, is very extensible and has a cute, context-dependent tab-completion setup. (The E editor for Windows is an approved clone, which uses the same language “bundles” as written for TextMate.) It’s 39 euros.
BBEdit is venerable. Don’t much care for it, myself, but it’s powerful and the Mac old guard swear by it. It’s rather expensive ($125), but there’s a stripped-down free version called TextWrangler that’s perfectly usable.
Smultron is free; I haven’t used it much. It has all the reg’lar features.
SubEthaEdit is for collaborative text editing. Sounds cool, haven’t any use for it.
For windows, I used:
E, as above. It’s as nice as TextMate and a good bit cheaper, too, at $35. Since Windows isn’t guaranteed to have some of the language utilities required by TextMate, E uses Cygwin. (In the background only. I think it can maintain its installation, if you—like me—have a distaste for Cygwin.)
TextPad. Haven’t used it in years, since my beginning programming classes, but I recall it being pretty extensible. I think it’s meant as an IDE replacement.
SlickEdit I used on an internship. Extremely expensive (can’t say how much), but fast, and has most of the bells and whistles to act as a general-purpose Java/C/Python IDE. I think there are Inform 6 and TADS packages running around for it, too, but it’s been a long time. Runs on Windows and Unix.
jEdit. The only Java text editor worth mentioning, really. I used it for ages. It’s very nice, especially if you’re using Java—but even if you’re not. If you know Java, it has Beanshell hooks, very convenient, and a nice macro API. Runs everywhere there’s Java.
SciTE shows off a text editing component for Windows and GTK, but is nice in its own right. Speedy. Configurable, but annoying to do so—be prepared to search through config files the option you’re looking for. It opens extremely large files quite well.