If you want a tough frame that pedals...I just got a good deal from
jensonUSA on an '04 Komodo. It was built as a heavy duty trail bike frame, has XC'ish geo so it pedals like a mofo...but it's only 3.9lbs.
I can't report on the durability-over-time b/c I just built mine
I sure do love it more than my dually though.
Oh yeah...and it's only $144