Which are the GNU Emacs modes/extensions you can't live without?

Question

I have been using GNU Emacs for as long as I can remember. The Emacs modes I use regularly are:

• Tramp
• Template
• Color-theme
• Python
• VCS
• SLIME
• Paredit
• Uniquify
• RCIRC
• Org

Which ones do you use?

Answer 1

For programming purposes these three modes are very helpful.

• blank
• light-symbol
• nxml

Answer 2

I often use the speedbar mode

Answer 3

I like

• org-mode
• gnus
• slime
• paredit
• ido
• uniqify
• regex-tool
• smooth-scrolling
• browse-kill-ring
• magit
• remember (in combination with org)

Answer 4

• gnus
• emacs-jabber
• DVC
• slime
• cc-mode
• org-mode
• nxml
• psvn/pcl-cvs/magit/......
• cedet (semantic/ede/...)
• w3m
• flyspell/ispell
• ...... ;-)

Answer 5

• gnus
• cc-mode
• flyspell
• iswitchb
• nxml
• pabbrev-mode
• saveplace
• csharp-mode
• bm (visible bookmarks in buffer)
• ruby-mode

And recently discovered:

• semantic-tag-folding-mode (part of cedet/semantic), gives you automated function folding in those languages supported/recognised by semantic. Much better than the old folding-mode.el
• which-func-mode - shows the name of the current function in the mode line

Answer 6

• gnus
• w3m
• AucTeX, preview-latex, RefTex combined
• maplev-mode (Maple REPL and code highlightning)
• flyspell
• tramp
• shell-fm (last.fm client)
• emms
• python-mode, ropemacs (python refactoring)
• nxhtml
• slime (for Common-Lisp, Scheme and Clojure, but it is mostly for fun)
• JDEE (Jave IDE) - I had some teaching in Java
• SVN-mode
• iMaxima (Maxima interface) It is really cool, but I mostly use Maple
• shell

Answer 7

Besides all of the ones listed, I've become a huge fan of yasnippet since I found it

Answer 8

I regularly use:

• nxml
• ediff
• vc
• tramp
• guess-offset
• smart-tab
• package (ELPA)
• ido
• debian
• ibuffer
• flymake
• recentf
• gud
• c, c++, python, makefile... etc. modes

Answer 9

log4j-mode for parsing log dumps

Answer 10

Most of the ones other people have specified +

• IPython
• Dired+
• ido
• tramp
• erc
• ECB
• ESS
• Eshell
• gdb

And sometimes when I'm feeling masochistic: Icicles

Answer 11

Most used:

• remember + my own logbook mode
• eshell
• vc
• notmuch/message-mode
• emacs-jabber
• python-mode
• erlang-mode
• tramp
• ido
• dired
• sql-mode
• eev-mode
• ...