Rumors are floating about on Twitter about Valve having something up their sleeve. At NeoGaf they've noticed a variety of big names tweeting about seeing something behind the scenes at GDC ending today. I'm going to assume there's an embargo right now, but it's a matter of what actually went down. Since we're seeing tweets all pointing toward Half-Life 3, but we all know that'd be too good to be true.
Saw Valve today. They have very nice things.— David Goldfarb (@locust9) March 29, 2013