What's your two favorite lenses in your camera bag and why?

With me it depends on the time of year.

At the moment I am going out a lot with just the DA16-45mm and the Bigma on my morning walks.  The 16-45mm does well for some nice early morning landscape / scenic shots and the Bigma for birds and other wildlife (also does well for some close ups and scenes at the 50mm end).

Summertime, when after butterflies and dragonflies I'll just take the DA*300mm and Sigma 105mm Macro, with a set of extension tubes.  Last year, the DA*300mm with a 31mm tube became my go-to rig for the large insects.  Easily handheld and manually focused.