After window shopping off and on for a few years, I finally pulled the trigger on my first build. I'm not a hardcore gamer by any means, but I wanted to have a decently future-proof machine that can play modern games at 1440p/60Hz at high settings while also making quick work of photo/video editing tasks.
The emphasis on photo editing is why I favored 1440p over 144Hz. Also, most of my gaming experience has been games like Skyrim and Fallout 3 on an Xbox 360 through a 1080p projector, which is an immersive experience I don't really want to give up, so I anticipated hooking up the PC to the projector and/or gaming with an Xbox controller at least some of the time—but I didn't want to sacrifice the ability to run games through a 1440p monitor at near-60 fps at near-max settings.
As for specific games/programs, my intended uses are things like Skyrim/Fallout 4 with lots of visual mods, Kerbal Space Program, GTA V, X-Plane 10, and Photoshop and other Adobe CS software.
CPU: i7 over i5 because I value the processing power for editing. This was a bit of a tossup between the i7 6700K and the i7 5820K; I went with the former as it seems like a better all-purpose CPU (i.e., I'm probably not going to be using multi-threaded apps often enough to tell the difference). I have't tried overclocking yet, but I'm looking forward to seeing what I can pull off.
CPU Cooler: Seemed like the popular choice these days, and a reasonable step up from the 212 EVO.
Motherboard: I wasn't really sure how best to choose a motherboard, but the Asus Z170-A seemed consistently well-rated and offered a good balance between price and features. So far, no complaints.
Memory: Basically just chose the cheapest 2 x 8GB DDR4 2400 I saw. I do especially like the visual simplicity of these sticks.
Storage: Seemed to be the consensus choice for balancing price and quality. I might add an HDD when I run out of space.
GPU: This was a bit of a tough one, but the R9 390 looked to me to be the best value for single-GPU 1440p/60Hz. I'd heard the 970 is a better value overall, but I'm willing to pay a bit of a premium to ensure a decent 1440p experience (and for double the VRAM). I ultimately decided I was willing to pay a little more if the R9 390X, so I waited for a decent sale on the Sapphire.
Case: I've always really liked Fractal Design's aesthetics. (I also wrote a Ph.D. dissertation about fractals, so I kinda have to. Hence, Mandelbrot.) This came down to the Define R5 and the Define S; I ultimately went with the R5 since it seems a little more full-featured (e.g., more front USB ports, more storage mounting options, and I might want to add an optical drive later), and I don't anticipate doing any water cooling. Non-windowed, because I'm more interested in sound dampening than showing off my build. I added a second 140mm front intake fan
Power Supply: 750W may be overkill, but it's a small price premium for the comfort of the extra headroom.
OS: I bought a Windows 7 Pro OEM DVD, then downloaded the Windows 10 ISO to a thumb drive and used the Windows 7 key to activate it. Worked like a charm--at least, after a couple of days of trying to figure out how to get a MacBook Pro to format a PC-bootable USB drive.
Monitor: This decision took a while. It wasn't long before I settled on choosing between the U2515H and the U2715H, but I had a heck of a time guessing whether I'd prefer the 25" or the 27". After waiting in vain for the 27" to go on sale, I decided the extra inches weren't worth the extra >$100, and that I'd prefer the high pixel density anyway. I'm generally pretty happy with that decision. There is quite a bit of backlight bleed, which is more distracting than I'd expected (such as when exploring dark areas in Skyrim), but the monitor is otherwise amazing. Between the picture quality, the build quality, and the aesthetic design, I'm really happy with this monitor.