This build was designed mainly for gaming in 1080p, specifically with games like Skyrim and Fallout 4 in mind. I also play BF1 on it. I didn't make much of an effort making it look good, I just bought the parts I wanted. My previous computer was a 3+ year old Dell Inspiron laptop (Core i7-3612qm, 8GB RAM, 500GB HDD and some crappy AMD laptop GPU). I was getting ~30fps in 1080p Skyrim with no mods on Low settings, so I decided to build my first gaming PC. This PC gets 60fps in 1080p Skyrim on Ultra settings with a lot of graphics mods (textures, meshes, weather and water mods, lighting, distant terrain, etc).
In general I tried not to cheap out on anything because I want this build to last. I don't want to have to upgrade this for at least several years, so I chose components that would not be obsolete for a long time, and tried to give myself room to expand in the future. So this is not really the most bang-for-buck build you can come up with, I'm sure I could have found a way to get the same performance for a couple hundred dollars less, but I'm OK with that.
CPU: I know this is a bit overkill for my system, I could most likely get the lower-clocked 4590 or 4460 or even something like an AMD FX 6300 and get the same performance since my GTX 960 would mostly be the bottleneck in games, but if I ever want to upgrade my GPU in the future I don't want to have to also upgrade the CPU. The 4690 should last me a while. I could have gotten the k-variant but since the 4690 is already way overkill I decided to save my money.
CPU Cooler: I actually used the Intel stock cooler for a while because I didn't know how loud it would be and I figured I wouldn't need an aftermarket cooler if I'm not overclocking. But man, that stock cooler is LOUD. My case doesn't have any noise dampening like the Define R5, and my headphones are not noise cancelling so I always hear this high-pitched whine coming from the cooler while gaming, which is super annoying. The Hyper 212 Evo gets recommended a lot so I tried that and it is much quieter, and my CPU temps are at least 10 - 15C lower than before.
Motherboard: This has enough features for me, obviously I don't need a higher end motherboard with overclocking and SLI support since I'm not doing either of those things. It even has an M.2 slot for if I want to upgrade my storage with an M.2 SSD in the future, although I don't plan on doing that anytime soon since my Samsung 850 Evo is plenty fast enough.
Memory: I'm not doing anything more than gaming on this machine so 8 GB RAM is good enough.
Storage: I wanted a fast boot drive since I was tired of the super-slow hard drive on my old laptop that took 3 minutes to boot up and log in, so I got this SSD. Now I can boot up and log in in about 30 seconds. 250GB was enough for me, but I also got a 525GB Crucial MX300 when I ran out of space on the 250GB drive about a year and a half later.
Video Card: I would have gotten the 4GB version but decided to save my money, since 2GB is good enough and should be good enough for a while. I've never had stuttering or frame drops or any other horror stories people in forums might tell you will happen if you don't have enough VRAM, I'm still getting a smooth experience in Skyrim with a lot of graphics mods, so I'm glad I didn't waste my money. Overclocking this card with MSI Afterburner was really easy, I overclocked the core clock 140MHz over stock and the memory clock 300MHz over stock, and saw a noticeable performance increase in Valley Benchmark.
Case: I didn't want a cheap case, I wanted something modular that also has room to expand, and is fairly dust proof. I got this on sale, normally it's more like 130$, and if it wasn't on sale I probably would have gotten the Rosewill Stealth or NZXT S340 or something, which is similar but smaller, but I'm glad I got this since it's fairly big, has lots of room to work with and lots of fan mounting options. I removed the middle drive cages since I'm not using them, to improve airflow. I plan on keeping this case pretty much forever, it has room for anything I might want to add to my system in the future (watercooling, more drives, fans and GPUs, etc) although I don't plan on adding anything right now. It didn't matter to me if I got the windowed version since I don't really care about showing off the interior (my interior isn't really exceptional-looking). So I got the non-windowed version since it was on sale.
Power Supply: I got the semi-modular version to make building easier, and so there aren't extra cables impeding airflow. Could have spent more on a 80+ gold one but I figured 80+ bronze is good enough so I saved my money. I know everyone says Corsair CX power supplies are crap but after two years it's still working good as new.
Operating System: Windows 10 got decent reviews so I decided to try it out on this new system, I used a USB stick to install it since I didn't buy a DVD drive (who needs DVD drives now anyway?) I like it so far, it's not much different than 7 (which I had on my laptop).
Headset: The Hyper X Cloud II is a very nice gaming headset. It's comfortable, the mic is removable, and the surround sound feature makes games sound really good, but remember to turn the surround sound option off when you're done gaming because the it makes music sound like crap. Being able to yank the 3.5mm jack out of the USB dongle and plug it into my Ipod is a really nice feature, and I also love that I only need to plug in one USB connector to my PC and it does everything, not like my old Turtle Beach headset for the Xbox 360 which needed a USB connector, a 3.5 mm jack for audio AND a separate 3.5mm jack for the mic all at the same time.
Monitor: This was on sale at Best Buy. I don't need anything better than 1080p 60fps so this is good enough. I might have liked a 27" more but then it would be more expensive; I'm happy with this. Edit: I bought a 1440p 27" monitor on sale on boxing day a couple years later. I don't game in 1440p but the extra screen space for other tasks is nice.
Keyboard: I've never used a mechanical keyboard, and while most people say mechanical feels better for gaming I don't think it's worth paying over 100$ just for better key switches. This is good enough for me.
Mouse: I upgraded to the Logitech G602 about a year after building this PC, and it works a lot better than the one that came with the keyboard. The higher DPI (max 2500) is nice for games like Elder Scrolls and Fallout which don't have very high sensitivity settings, and the extra buttons are useful. I can't believe how much easier settlement building in Fallout 4 is with the Enter key programmed to one of the thumb buttons on the mouse. Having R + Enter also makes scrapping items much faster. Mapping backspace, copy and paste to other buttons also made coding easier. I really like not having a cable to worry about, and even though it's wireless it still performs perfectly, with no issues so far. It's a little heavy and that took some getting used to, but after a few days I'm accustomed to it and it feels good now, and although it can take two AA batteries you can luckily use it with only one battery installed to make it a bit lighter.
I got the USB Front panel thingy a while after building this because I moved the computer from the top of my desk to the compartment under my desk, but the case is so big there was no space to plug in a USB stick because the front panel USB ports on this case are on top, not in front. Might have wanted a slightly smaller case in retrospect to fit it under the desk more easily but I wasn't thinking of size at the time.
I got a cheap cloth mouse pad for 7$ and it works very well. Ridiculous 80$ so called "Gaming" mouse pads are not worth the money imo, and will not make me better at gaming, no matter how many RGB lights you put on there (Razer I'm looking at you).
I got the monitor and 850 Evo SSD at the store, the rest was ordered online. These prices do not include shipping or taxes. These are the prices that I paid at the time, so they won't be the same as the current prices.
All in all I'm very happy with this system. Building it was a lot fun and I learned a lot while doing it.