Open anything with Spotlight

Press ⌘ + Space and a search field opens in the middle of the screen. Type a few letters of what you want and press Return.

For launching apps it beats hunting through the Dock or the Applications folder: three or four letters are usually enough. It also searches inside your files, so you can find a document by a phrase you remember from it rather than by its name, and filter by typing something like mp3 to see only that kind of file.

It doubles as a calculator and converter — type 125*4 or 30 usd in eur and the answer appears in the results without opening anything.

Two habits make it stick. Trust the first result: Spotlight learns what you open and puts it on top, so ⌘ + Space, two letters, Return becomes muscle memory. And use it instead of the Dock for a week — after that, a Dock full of icons stops feeling necessary.