Usually in my camera bag, I would definately have a F2.8 24mm-70mm lens which is my most convenient len, able to capture group photos and even nice portrait shots. My flash light SB 910 is a must for low light shots and for fill-in shots too.
For event branding photography, I would bring 2 additional lens. My favourite Nikon F2 135mm Len and a Nikon F2.8 70-200mm Len to capture shots that are quite a distance from me. Like shots on a stage or shots that I didn't want people to know I am shooting them. Just have it candid and natural. And of cause lots of spare batteries
For leisure walkabout and I want to carry light, I would bring my Nikon F1.4 50mm.
In addition to all these, I would have my personal items like my hat, tissue paper, selfie stick, wallet and my beloved iphone 6
Branding portrait of Blogger Nicholas Lin using Nikon D800 with prime lens 135mm F2 ISO 100 1/500s.