Enso
Having to change programs to perform simple tasks—for example, making a quick calculation, or looking up a definition—breaks your concentration, takes you away from the task at hand, and wastes your valuable time. Enso lets you do common computing tasks easier and faster than ever before. You get a huge productivity boost and a simpler digital life. And now that Enso is free, it won't cost you a penny.
Turning Caps Lock into a command key might sound strange at first — no other software works that way, does it? — but our philosophy is that interfaces can't hope to be better than what you're used to unless they're different from what you're used to. You'll find that Enso is different in a lot of other ways, too. Give the Caps Lock method a try. If you don't like it, you can of course configure Enso to be activated in the way you prefer