IDE with AutoCompletion?

Here is a list of LaTeX IDEs

While emacs+AucTeX doesn't have "autocompletion" per se but it does have something that performs the same role, and performs it better (obviously).

Let's take the example of adding section headings. With autocompletion I start writing \sec... and then press TAB or some such autocomplete key.

With emacs, you press Ctrl+C and then Ctrl+S and emacs asks you what level of sectioning you want. You type sec... and then TAB to autocomplete. Then emacs asks you how you'd like to label that section (I want to call this section foo). It automatically adds a \label{sec:foo} below your \section command.

Fine. But here's the really useful part. Let's say you want an environment: Ctrl+C then Ctrl+E. Then emacs asks you what kind of environment you want. And if you tell it you want an environment emacs understands, like minipage it will ask you for its compulsory arguments (width, for minipage). It will then create the environment and put you between the \begin and \end tags.

More cool features of emacs: abbrev-mode which is basically auto-complete on magic!

And the smart ` : Typing ` then a gives you \alpha likewise for other greek letters. ` then pressing the right arrow key gives you \rightarrow Likewise for other arrow directions...

Also, you get like, 100 geek points just for using emacs. Fact.

TexnicCenter in windows also has a completion function with Ctrl+space and additional custom commands can be added in xml files in the TexnicCenter program folder

TeXworks has some builtin autocompletion, but take a look at the script autocompleteForTexworks. The script can perform completion on long words earlier used in your document, labels and filenames for \input, \include and \includegraphics macros.

There is a video of it in action on youtube.

Guide to use.

1. start typing the long word that should be autocompleted
2. press Crtl + M and the autocompleter will complete the word or at least make a suggestion for a completion.
3. if not satisfied with the suggestion press Crtl + M until the correct word is found.

Disclaimer: I'm author of the autocomplete script.