Best choice for first/only prime on 6D FF?

Thanks so much everyone. With all these great prime suggestions, and little love for the 24-105, I think I'll forego the latter and aim for 2 primes, one of which may very well be the 100 f/2 or 85 f/1.8.

Good point above about needing a wide lens at 24mm. As long as I have the 24-70, I wasn't worried about that. But then that's sort of contradictory, as I'm asking for a general walk around lens and it's precisely because the 24-70 Mk I is so big and heavy that I don't want to walk around with it...

Lots to think about! It's easy to get obsessed with photography, isn't it? I'm just an enthusiast, and because of time/budget need to keep it that way...