My first lightning shoot with my 6D. I usually use my 550D with my Tokina 11-16 f2.8 because I trust that lens at infinity more than any other lens I have owned and I usually shoot lightning that way. Maybe I am doing something wrong but the other lenses that I use for lightning namely my EF 50 f1.4 and EF-S 15-85 f3.5-5.6 don't seem to be sharp at infinity.
These were shot using my EF 16-35 f2.8L II at 35mm. I focused on the tree line. Sadly the sky wasn't completely dark so I couldn't do long exposures and the nice colors in the clouds that come with lightning were muted somewhat. I like how they turned out and love how the files can be worked in post without the banding and other issues that I would have with my 550D.
See more at: www.flickr.com/toodamnice
3.3 seconds, f10, iso 100
4.3 seconds, f10, iso 100
2.7 seconds, f10, iso 100
8.3 seconds, f10, iso 100
2.9 seconds, f10, iso 100
5 seconds, f10, iso 100, cropped