Helvetica
I've gotta admit, I'm not typically a Helvetica person. The "hallmark" of a Reilly Hamilton designed site is Gotham. Gotham everywhere. Gotham Black logo, Gotham Medium navbar, etc. The other "tell" is the gradient. Oh my, do I love gradients. Just take a look at current "working" Nexus logo. It just screams "Reilly".
But I'm trying to take a step back from my typically "busy" layouts of yesteryear and do a nice, clean simple "Web 3.0" layout. This means large white spaces, not-black blacks, thin dividers, and Helvetica. I've been using Google+ and the new Gmail theme as my inspiration.

