I really really like the ability to search apps with a few keystrokes and I really really like to be able to search clipboard history with another few keystrokes.
Nothing I've found are doing both or one as good as Alfred.
GNOME does this out of the box. It's possible to add this to e.g. StumpWM, i3 or AwesomeWM too.
Similar functionality is available in emacs with Helm: search through all callable functions by just typing a few characters.
> I really really like to be able to search clipboard history with another few keystrokes
Emacs does this, with yank-pop (M-y); Helm turns this into helm-show-kill-ring, which offers extremely convenient searchability.
I really can't recommend emacs highly enough: it's everything one could want in an operating environment.
* For searching and browsing, Listary Pro is pretty good.
* For text expansion, AutoHotKey
* Automating, maybe AutoHotKey again.
* Clipboard stuff - Ditto, Clip X
As I mentioned in another post, Scott Hanselman's giant developer tools list is particularly useful:
http://www.hanselman.com/blog/ScottHanselmans2014UltimateDev...
http://www.ghacks.net/2014/09/24/activaid-is-a-useful-autoho...
I haven't tried it, but Albert may be worth a look : https://github.com/ManuelSchneid3r/albert