[amyjess]

Noto. It feels like having access to an entire professional foundry as a FOSS download.

Though the sans is humanist and not neo-grotesk like Helvetica.

Hell, Noto Sans is available in more weights than Helvetica Neue LT Pro. I've actually found myself wishing that Helvetica Neue LT Pro had a real demi instead of jumping from medium to bold. Noto solves that problem.