So my favorite go to san serif is Myriad Pro (especially the light face). I love it's clean lines, it legible characters and it almost melodic flow - especially compared with the standard of san serif fonts, Helvetica. There's another face that I think is also fascinating, simpler and more modern looking than Myriad: Phoenica designed by Ingo Preuss. Arguably, because it's more simplified, it's not as legible as Myriad, for instance the lower-case a has no tail the lower case g has no ear etc... But the face maintains a lovely, albeit, subtile, rhythm. I'm looking for a project to use this face.