This is a great question, and one to which the answer is ALWAYS changing. Of course there are a few core pieces of equipment that never really changes, but I am constantly updating my equipment and adding more!
Right now, this is what you will find in my bag(s):
Nikon 24-70 f/2.8
Nikon 70-200 f/2.8
Nikon 105 Macro
Sigma 35 f/1.4 ART
3x Nikon SB800s
A bunch of Photix Strato II transmitters & receivers
Tripods, Stands, Light Modifiers:
Manfrotto Tripod, several Manfrotto light stands in different sizes, a Manfrotto Background Stand, several umbrellas & soft boxes, all of which are very portable!
More than I can possibly need of the fastest cards SanDisk has to offer, ranging in sizes from 8GB to 64GB
Rechargeable Eneloops for anything that requires AA or AAA batteries, and original Nikon Batteries for the cameras.
My two main bags are a Lowepro x200 and the Herritage bag from Shutterbag (it’s so beautiful!). I also have a Shootsac but that doesn’t get too much use anymore.
I think that covers the important stuff. I can’t wait to see what makes it to the list next, I already have a few ideas!