This one is a bit meta: but I like to keep my Emacs customizations (those made through customize) in a particular file, which resides in a location that is periodically backed up.
(setq custom-file "/my/real/custom.el")
I then load this at the top of my init.el file:
(load "/me/real/custom.el")
Sure, I could have just symlinked the default file location, but I prefer doing it this way b/c then its documented with the rest of the config.
Not like I find myself browsing assembly all that often (though, it isn't never).
No. Instead I mention asm-mode to point out something very general about emacs: it's the original "batteries included" programming tool. I appreciate that, no matter the file format I want to look at, I can be fairly confident that emacs will have a built-in way to make sense of that file. Assembly; C/C++, Java, Python, Ruby, Perl, Lisp, Shell ...
Browse your OS's installed info pages from the comfort of Emacs. I'm using it right now to browse the #elisp manual.
The info system is a hypertext mini-web available on most unixy OSes, and is primarily used to supplement man pages, often with more of a tutorial style.
Very handy when you want a refresher in some old hacker's ideas about how something should've worked 30 years ago. 😜
Creates a new detached OS window (called a "frame" in Emacs parlance) running Emacs. That's right! You can have as many Emacs windows running at once as you like, all of them sharing the same Emacs session! I do this at work: a single Emacs session shared across three monitors - all fullscreened. I almost forget that I have to use MacOSX...
You can switch between frames using M-x other-frame. One for my agenda, one for the papers I'm reading, and another for my code projects. Never touch a mouse again!
A full featured #irc client built into Emacs. Back when IRC was the world's killer app, erc was my absolute favorite client. It remains so today. You can even use it as a kind of "bumper" system: just run emacs inside of a #tmux session on an always-on network host, fire up erc, and #ssh into that machine whenever you feel like chatting.
Enabling the minor mode visual-line-mode toggles on nice-to-look-at word wrapping in your buffer. I use it all the time when writing long documents. Some may protest, saying that there is always M-q aka fill-paragraph and friends, but sometimes you do not want to artificially insert newlines into your text. With visual line mode your newlines are placed just where you intend them to be.
I use this snippit to create a faux light mode for whatever dark theme I'm using. It doesn't work on all systems (does nothing on my Mac at work, for example), but I've had other Linux users try it to firm results. So if you like the theme you're using but wish it had a "lighter" variant, this is a way to fake it!
So you've been horizontally and vertically splitting your windows and now you've got a mess? No worries: M-x balance-windows has you covered. It tries to redistribute screen real estate equally among your frame's windows.