Itsy is a basic Twitter app for your OSX desktop. It is the antidote to all the professional, complex and resource-hogging apps out there, and focuses just on the basics of tweeting.
Itsy has a really cute icon, which after installation will sit happily in your dock, and a miniature version also appears in the menu bar. Itsy's interface is super simple, with your feed appearing in the main column, below buttons for direct messages, @ messages and a search.
Like other Twitter apps, Itsy indents your own tweets on the opposite side of your feed, so they're easy to pick out. Links open in your default browser. It images can be viewed inside Itsy, and works with Growl notifications.
Itsy doesn't do anything special with Twitter, but it's lightweight, covers the basics and has a cute icon.