The Guardian uses Helvetica… judge yourself if that is overused. Why should it be thick and chunky? Lighter weights are probably more legible from a distance, which might be a thing to consider when selecting type for signage.

nope, that would be Guardian Egyptian designed by Christian Schwartz and Paul Barnes.

http://www.myfonts.com/fonts/fontbureau/farnham/

Farnham, is also by Christian Schwartz, but those inktraps might be too obvious at signage sizes.
Or
http://www.myfonts.com/fonts/dtptypes/vigor-dt/

http://www.myfonts.com/fonts/emigre/fairplex/

Tim

Aptifer Slab was recently released by Linotype and looks promising.

Good choice.

FF Info was designed for wayfinding.

hey i like Aptifer.. just how i imagined it. thanks

SOPHISTO, has a lot of different weights and alternates. Also arrows and other dingbats.
Have a look here; http://www.macrhino.com