For 7/12 or less, skater shoes have always been my favorites. Vans, DC, Airwalk.. there are a range of options out there. They stick like glue, as they are designed to do on the very similar asphalt grip tape on a skateboard deck. DC makes a really nice high-top style that gives good ankle support. If you don't get overly showy or colorful shoes, you can still appear professional, and you don't have to change your shoes every time you climb a ladder. Once it gets any steeper, or you are forced to use ropes, it's time to break out the paws.