http://proxlet.com/ http://proxlet.com/ lets you do this. It's not a Twitter client, it's an API proxy, most prominently used in a Chrome extension for Twitter.

http://proxlet.com/ http://proxlet.com/ lets you do this. It's not a Twitter client, it's an API proxy, most prominently used in a Chrome extension for Twitter.com. I built something very similar with http://slipstre.am/ http://slipstre.am/ though without client filtering. In 6 months, no one has asked for it. Pattern filtering seems to be good enough (e.g. block tweets containing "4sq.com" vs. tweets from the "Foursquare" app).