I currently use Canon cameras including the Canon 5D Mark III, Canon 1D MK II and Canon 7D. The majority of lenses are "L" series lenses, including 300mm f2.8, 70-200mm f2.8, 24-70mm f2.8 and 17-40mm f4. My most utilized lens for Landscape is the 17-40mm. The 300mm f2.8 is my primary sports lens.
Thoughts on Gear:
I believe Nikon, Canon, Sony are excellent. I selected Canon since Canon has a local service center in Costa Mesa, CA. I shoot at least 50,000 photos a year so I knew I would need to have my gear serviced on a regular basis. Sony is really making waves with their new Canon A7 line of cameras. The Sony's will be a serious contender for my next Camera body.
Invest in Glass:
Good quality camera gear is not cheap, however purchasing good quality lenses are well worth the investment since the image quality will be much better, good glass also holds it's value. Purchasing used quality glass is a good value if you understand the risks and purchase from reputable suppliers. I have had good and bad experiences purchasing used lenses - however mostly good. I have one lens that is 16 years old works perfectly. The lens has several "drops" under it's belt and still keeps on clicking. I can also sale the lens for nearly what I paid for it (I bought it used 10 years ago). In my opinion if you take care of your gear buying high quality lenses is a no brainier.
Recommended "Minimum" Lenses:
Landscape: Canon "L" 17-40mm f4 or Canon "L" 16-35mm
Sports: Canon 70-200mm f2.8 "IS" or "NON-IS" - either one is worth every penny
General/Walk-a-round lens: Canon 50mm f1.8 or Canon 50mm 1.5mm.
*In my opinion the f2.8 lens is essential for sports due to low light situations. You may get away with using a f4 lens if you have the latest Camera Body (Canon 7D MKII , Canon 5D MKIII however in my opinion if you want to maximize the opportunities f2.8 is essential.
Recommended Camera Bodies:
Landscape: Canon 6D - full frame and a great value!
Landscape "Pro": Canon 5D MKiii - prices are dropping fast.
Sports: Canon 7D MKII - GREAT camera and a great match for the 70-200mm lens.
Sports "Pro": Canon 1DX - nothing better! I use a Canon 5DMK3 and VERY happy with the images - great "Dual" purpose camera.