Wrangler's "Riggs" line of cargo pants are my go-to.  I used to wear the Duluth firehose pants, but I grew to hate the pockets on those.  The Riggs pants hold up to abuse nearly as well, and I find them more comfortable and better designed.  The front of the legs is actually two layers of fabric, so if you wear through the outer layer of the knees, they're still usable, albeit no longer suitable for formal affairs, coronations, royal weddings, and such.