If you can squeeze it into the budget, the 12-35 2.8 is really wonderful. That's pretty much the only lens I ever use on my G7 these days.
There are a number of C-mount lenses that'll cover the 4/3" sensor quite nicely. I believe they're made by Fujian. The 35mm is my favourite. It isn't a stunningly sharp lens, but it's fun to use once in a while.