Here’s some stuff I like:

AutoComplete is helpful for programming as it picks out words like function names and things. It doesn’t try to parse a programming language (I don’t think) which has the advantage of seeing through language mixtures or unsyntactic constructs. Its popup menu is a little unusual at first but works well enough. Unbind the up/down arrow keys to avoid spinning through completions when you wanted cursor movement. Completing numbers is often not useful, not unless there happens to be just a few repeating throughout your document. I imagine that could be restricted. Filename completion is sometimes a little too aggressive, and if it hits a big directory is slow stat()ing the whole lot (multiple C-g gets out, or I’ve been trying a little no-stat variation which might eventually come to something presentable).

WhizzyTeX lets you crunch just a section of a big document for speed, or whole-document. Its version 1.3.2 has a minor problem of (goto-line error-begin) which mucks about with the mark when it shouldn’t, and the default error faces have poor contrast on dark background but can be customized in the usual ways. Its idea of real-time is too quick too, as it likes to update on every keystroke where it would better to hold off for maybe 1/3 second or so of quiet. I notice this when changing widths and similar in pgf pictures. A quick backspace and new digit redraws for the backspace then again for the new digit. If the backspace puts a size or scale to zero this can be disconcerting. There’s some time and CPU load hold-off stuff in whizzytex.el, but can’t tell if such a delay is what they’re meant for. Oh, and Emacs 25 flyspell and whizzytex don’t go together, the symptom being input keystrokes lost intermittently when both enabled. Dunno why (but in Emacs 24 they’re ok).

Stuff by me with its own page here includes: AlignLet, Chart, DiffSaveBuffer, GtkLook, GutenbergCoding, HtmlCoding, InfoXref, MakeinfoInfo, ManPreview, MoMode, NobreakFade, Pcf2Bdf, PerlPodCoding, PerlPodGt, PerlPodPreview, QuickYes, ShAutoconf, TexMathPreview, TtyFormat, XmlCoding, XTide. Or see my site map full list.