Hmm, well, you are certainly running the gamut of possible things to do with a camera. From what you list, you would be served well by fast burst, strong low light capability and solid weather sealing. Certainly the high end models by either Canon or Nikon would fit your needs nicely, though it may also be worth considering starting in the middle of the market and investing in optics instead.
It really all depends on your budget, but mid-range cameras in Canon and Nikon's lines will be a little more forgiving since they are APS-C rather than full frame for getting started (the depth of field will be wider and shorter lenses will give you more apparent magnification.)
Camera bodies get significant upgrades far more often than lenses, and you will benefit from both good optics and good lenses. When I started out, I actually started with an entry level DSLR from Canon and then invested several thousand dollars in lenses prior to moving up to a Canon 5D Mark iii (which is the next to top model).
So, starting with a mid-range body lets you have a slightly easier camera to use (though not capable of quite as nice of photos, but still pretty spectacular) and leaves more funds available for getting high end optics. Then later on down the road, you can upgrade to a higher end body and have all the optics you need already. It's also then handy to have a backup camera body around if anything goes wrong with one or to be able to have two different lenses mounted at any one time.
EF lenses are compatible with any EF mount camera, you just would have to avoid buying EF-s lenses if you want to move to full frame cameras eventually because EF-s is not compatible with the higher end, full frame camera bodies like the 6D, 5D and 1D.
As far as Nikon vs Canon, there isn't a significant advantage either way. Currently on the high end the D800 has slightly better low light and a wider dynamic range than the 5D Mark iii, but the 5D has better third party software support with Magic Lantern allowing for some cool things to be done with it, both are excellent cameras overall though and Canon and Nikon are a constant back and forth. It really comes down more to system preference and which camera layout you prefer. I'd suggest trying a Canon and a Nikon model out in a local store to see which you prefer since they are pretty consistent in feel across the entire line.
The one other thing that might be worth considering is Pentax. They are a minor player in the field compared to Canon and Nikon, but they make the most weatherproof options around, especially within a cheaper price range, so they might be good for your outdoor, bad weather shots, even though something like a 5D would do fine, particularly with a rain hood. I don't personally have any experience with the Pentax systems, but we do have people on this site that use them extensively.
Also, as a few other people have mentioned in comments, it's really hard to make a "wrong" choice, particularly when starting out. Just about anything you get is going to be a major step up from any point and shoot and they all work similarly enough that if you learn the basics on one, you can switch to another if you find out you like things a different way, you just might have to sell off your lenses to buy in to a new system, but that's not a big deal until you have a big set of lenses and resale values on lenses are usually pretty good if you treat your gear well.