I think all all love fonts should play: http://cheeseorfont.com/ Also, I love Aerial narrow if I had to choose (or other random fonts that I use on photoshop). It used to be Papyrus but then it was overused.
Century Gothic. Still, whenever I have to do a project for school, I usually use Courier New. I'll admit, it's sort of grown on me.
inb4 some hipster says Helvetica But yeah, for design I absolutely love the Futura and Times New Roman fonts. To use in conversation I like Calibri or Tahoma.
I am using it right now: sans-serif. Gentium Plus gets an honorable mention for having been my default system font for over a year.
It changes a lot haha. Lately I've been quite a fan of Rockwell, though it's best reserved for the odd header; Helvetica (yeah, I did it) and Ubuntu are my favorite sans-serifs just because they're so versatile. I'm not a big fan of serif fonts because I think they're overlauded and overused, but my favorites from them are probably Droid Serif, Copse (though it has a bit of a flair to it), and Gentium (usually do my school reports in this P: ).