I've been a Canon user ever since the early days of digital. I now work mainly with the Canon 1DX body coupled with the highly flexible EF 200-400mm IS lens which includes a built in 1.4 extender.
Other essential items in my kit bag include:
Canon EF 70-200mm f/4L IS USM (much lighter and just as sharp as the f/2.8L)
EF 16-35mm f/4L IS USM (great for all wide angle work)
1.4x and 2x Extender Mk III (an ideal way of getting extra reach without compromising on image quality).
Gitzo 3532LS Systematic Tripod and Uniqball Head
Think Tank Bag Glass Limo and Airport Accelerator (light, rugged and adaptable)