I've been using this Sigma 35mm, 1.4 now for a few weeks. It has become my go to lens for walk around.
This is Downtown Las Vegas after dark during the Fremont light show.
ISO on Auto (ISO200 here), Shutter priority at 1/100 sec, Aperture at 1.4.
DSLRs: Canon 5D Mk III, Canon 60D
Lenses: Canon 16-35 F/2.8L, Canon 70-200 F/4L, Canon 300 F/4L IS, Tamron 90 2.8 Macro, Tamron 24-70 DI VC, Sigma 35mm 1.4 DG
Flash: Canon 600 EX(2), Canon ST-E3-RT, Alien Bees B800