I tend to use Papyrus or Impact, depending on the project.

Yep, looks like all of us are on the Lato/Source Sans Pro bandwagon. Monteserrat is nice too.

• Source Sans Pro
• Open Sans
• Proxima Nova
• Museo Sans
• And many more sans typefaces...

As for UI font choices, I'm currently digging these:

• Avenir
• PT Sans
• Apercu
• Runda

I like this article on the topic: http://typecast.com/blog/type-on-screen-5-faces-for-ui-design and this one: http://www.design-by-izo.com/2011/10/18/what-should-i-look-for-in-a-ui-typeface/

All we're doing is avoiding Helvetica Neue (a popular font for a good reason) and congregating around PT Sans, Lato, et al.

You only have to look at Font Squirrel to see how this trend is pretty widespread. A few months from now a different user is going to write a similar post but replace "Helvetica Neue" with "Source Sans".

Roboto, is a great clean typeface

H&FJ Whitney is super nice and with their ScreenSmart thing it renders amazingly well on screen. Other than that both Open Sans and Avenir Next are superb choices.

For the Hightail redesign I chose Verb, which has proved surprisingly adept.

Serifs: • Gentium • Neuton • Merriweather • PT Serif

Sans: • Open Sans • Oswald (for headlines) • PT Sans • Source Sans Pro

I've been using Aperçu as an all-purpose brand typeface at Floored, with FF Yoga in a supporting role. (Took me forever to find a serif face that'd play nicely with Aperçu, though.)

For me, Segoe is the new Helvetica. Lato for header related.

I love Atrament Web (https://typekit.com/fonts/atrament-web). It goes great with Proxima Nova (https://typekit.com/fonts/proxima-nova) as well!

A current favorite of mine is Open Sans. Free, embeddable, lots of weights.

Open Sans is pretty trusty

Helvetica Neue with Arial as a fallback. They're nice, readable typefaces – there's no reason to use something different just because they're popular.

That being said, I have a penchant for nice condensed/tall geometric typefaces for headers, i.e.:

Trade Sans

and DIN-based faces for number-heavy interfaces, i.e:

DIN Next Pro

Proxima Nova and Open Sans do the job for me.

I really like Montserrat. It's one of my favorite fonts at the moment. http://www.google.com/fonts/specimen/Montserrat

comic sans

Depends on the interface in question. At the moment I'm using Source Sans Pro because it's ever so slightly condensed and works well in narrow table columns.

I've been a fan of Avenir on iOS. Looks great on Retina and adds a human(ist) touch to a UI, if it needs it. Helvetica Neue can feel cold and functional so it can be a nice alternative at times.

There's a lot of nice fonts mentioned above. I'll add a few favourites: Gotham and Museo Sans are beautiful geometric sans-serifs with a wide range of faces from light to bold.

Anyone has ever used (or seen) Brandon Grotesque as a primary face for iPhone app?

Whoops, I should have written "Ask DN" in the topic title.