Windows/Mac/Linux: When it comes to notes apps, you have a seemingly endless trail of options, but it's rare to find one that's cross-platform, supports the Evernote-style of rich notes, and works without needing an account somewhere. Collate is just that.
The idea behind Collate is pretty easy to get behind. It uses an the now standard "big notes app" organisation methods of notebooks with individual notes inside. Those notes can be Rich Text, Markdown, an outline, or a web clipping Organisation is done with the aforementioned notebooks as well as with tags, but you can also just search for anything you need. Collate even supports syntax highlighting, which is great if you save lines of code.
Most of that is standard these days, but Collate also saves all your notes on your computer in a format any computer can understand outside of Collate. Nothing is locked into the app or hidden away in a database. Likewise, everything stays on your computer.
This means you miss out on any type of syncing function unless you manually choose your a folder in something like Dropbox to save those documents. It does, however, mean you'll always have full control over those notes and they never go some server that you don't want them to.
Collate is pretty early in its development, so it might be a tough pill to swallow for $US20 ($27), but you can check it out for free during a 14 day trial to see how it works for you.