OS X. Social network aggregator with full support for Twitter (searching, etc). A social app thats integrates Flickr, Facebook, Twitter, Identi.ca, Digg, Reddit, RSS and Google Reader all in one great place.
Bought this app a couple of weeks ago. It works beautifully bringing in your Twitter, Facebook, Flickr, Reddit, Digg and Google Reader. My favorite part is being able to make smart folders for Twitter. I have my News all in one folder, local news in one, sports, etc. It definitely helps those who follow a lot of people.
I used Eventbox for the trial period, and I think it's one of the better clients out there. It's a native Mac-client and that makes it all the more desirable. It's well designed and works. It's of course, beyond, just a Twitter Client. Brings in your Facebook, Flickr, (and other social apps) and G-Reader all in one "box" *and* integrates them.
If you haven't tried it, you should. Really should. I'll probably shift completely when they have (a) multiple twitter accounts and (b) share with notes on Google