My most used lens, the 24-105, had a hard encounter with my tiled floor and is now a paperweight.
I am debating the following:
Buy a new one (alternatively the Sigma 24-105 which is about 200 $ cheaper than the Canon in my country)
Buy a 24-70 (probably the Tamron SP 24-70mm F/2.8 Di VC USD)
and a Canon 70-200 F/4 IS and sell my Sigma 100-300 which I don't use much because of the weight.
I really like IS on my zoom lenses and I don't like carrying around a lot of weight.
And by the way, my 6D is the camera I use almost exclusivly.