System Usage from Most to Least Important: Gaming, and gaming only
Parts Not Required: The mouse and keyboard
Preferred Website(s) for Parts: Newegg.com
Parts Preferences: No Preference
SLI or Crossfire: Whichever one will be compatible with the parts.
Additional Comments: I am a complete noob when it comes to building a computer, I don't know anything about which parts go with which, this is my first time building such a computer. I would like to have a computer which can run ARMA, Skyrim, GTA and such games with no issues. I'm willing to spend a couple of extra bucks if there is a better part out there for it.
i5-2500k 219.99 (If you have a microcenter around buy from there for substantial savings)
Any Z68 or P67 board, there's virtually no difference in the overclocking potential of these boards, so find one that supports the features you like.
Any 2x4 GB DDR3 kit that is on the motherboards Quality Vendor List, again this is a decision that for typical users makes virtually no difference, just make sure it's a compatible kit.
6950 1GB for the games you listed. If you want to run more graphic intense games like BF3 or Metro 2033 at the higher settings then a 570 is the entry into that segment.
Depending on your graphics decision pick a psu that supports the number of pci-e power connectors needed (6pin, 8pin ect). You can find that information on the gpus detail page. Stick with name brands like Corsair, Antec, PC Power and Cooling, ABS, Silverstone. Try to find one with a single 12v rail and 80+ certification.
Case, the most important thing is to ensure it'll hold your video card and heatsink/fan. Most modern mid-tower cases and larger do, but double check with the forum if you're unsure. Opinions on cases rage across the board but as long as you stick with a quality vendor like Antec or Cooler Master you'll typically be fine.
HDD: Right now the only HDD I feel even remotely comfortable recommending is the Seagate 500GB for 84.99 at newegg. The prices on these things have skyrocketed due to flooding in Thailand and until the prices come back to a reasonable level there really is little incentive to spend any more than you absolutely have to.
SSD: With your budget you could probably squeeze a decent SSD in there to act as a boot drive and still be large enough to stash quite a few games. At this budget I'd be looking at the 120GB drives that are based on the Sandforce 2281 controller. I typically recommend the OCZ Vertex 3 as I own OCZ drives, can attest to not only their quality but the topscale level of support you get on their forums.
DVD: Most people typically only spend about $20 here. The Asus DVD-RW is probably the single most common component in most builds. If you want to do something extra like Blue-Ray playback just make sure that the drive ships with BD encoding/decoding software otherwise you'll have to buy it separately in order to have this functionality.
I probably forgot a thing or two, and I know it isn't a part by part list, but I'd rather see you look into some of the things mentioned so that your knowledge of the parts grow. The more you understand what it is your buying the more confident you'll be that you've made the right decisions, and the more you'll understand your rig once it's ordered, built, and running. Good luck with it.
Basically, get a p67/z68 motherboard, i5 2500k, gtx 580, 8gb ram because of the insanely cheap prices at the moment, an 800w ish psu for sli later, and a 500gb hdd at 7200rpm, choose your own parts for the mobo, ram, psu by looking around and your set!