Any recommendations for shooting deer (haha) with the DSLR? What lens would you use in a forest for capture deer, pigs, coyotes, etc at distances between 15 yards to 60 yards. Obviously this will be pretty low light conditions most of the time as well.

Would 600mm F2 be enough? thoughts? What do I need to be thinking about before bying a lens.

Going on Nikon D750

600mm F2 a myth of a lens. Would weigh a ton and cost a bomb if there ever was such a thing.
In my experience with wildlife video a zoom should be your lens of first choice, as it will accommodate subjects of different size and distance.
I have a Sigma 150-600 on my Lumix GH5 and I mainly shoot birds. In South Africa recently while videoing mammals in the Kruger Park my 100-400 lens came in handy.

Ron

ps don't worry much about maximum aperture. You'll be outside in daylight. I often have to use ND filters on what a stills snapper would consider to be "slow" lenses.

What about during super low light situations? What's the minimum aperture I need.

Thanks in advance for the help.

Tobin, you are right. The more light you capture the better. Don't forget that on the forest floor you can sometimes have only a few percent of the light that would be available without trees. I usually film with a 200-400mm f/4 lens, but for low light conditions I have a 300mm f/2.8 and a 200 f/2.
In my opinion you better have a wider shot with f.e. a 200mm lens that is well exposed, than a closer shot with f.e. 400mm which is underexposed or pushed up with higher iso. Noise is your enemy with slow lenses.

You should buy a lens which covers majority of your shooting type. If you are always shooting low light, then better to buy a 300 f2.8 or 400 f2.8 lens. Later you can add more lenses depending on requirement.