I built this computer to be a no-frills, reliable gamer that can handle anything at 1080p at the highest quality settings. Nothing fancy, no fussing with overclock stability or thermals, just power on and game.
CPU: I decided to get a low-end i5 over an AMD FX-8350 mostly because I could get a basic Socket 1150 motherboard for less money than an AM3+ motherboard, which made the Intel solution more affordable. I'm not overclocking so the stock cooler works fine, which is also not the case for AMD, whose stock cooler is exceptionally loud. Going quad-core provides good performance in CPU-intensive games like BF4, where dual-core Intel CPUs tend to struggle a bit. For me it was worth the extra $60 over an i3.
Motherboard: There was no point in getting a fancy Z87 or Z97 board for a locked CPU. For the purpose of this system, I didn't need features like RAID, SSD Caching or M.2 either. The H81M-P33 is a nice reliable board that has just what's needed. You'll need to upgrade to the latest BIOS for full Haswell Refresh compatibility.
RAM: I would normally have gotten some A-Data 1600 MHZ for 10$ cheaper, but I could not find any in stock locally, and having some shipped to me would have eaten up the savings. So I bought this Kingston RAM instead. The blue looks good, so I'm not unhappy with it, and it's performed very well.
Storage: Some people here knock the Kingston V300, but I have found it to be an excellent SSD value. It's not quite as fast as a Samsung 840 or Intel SSD, but it's pretty good (see picture of ATTO benchmark). In everyday use, I can't really tell the difference between the V300 and a Samsung 840. The Seagate Barracuda 1TB rounds out the storage for games and music.
GPU: The price was pretty good on this XFX R9 280, especially with the game bundle. It's a re-numbered Radeon 7950 with a 7 MHz clock speed boost. The XFX model has a well-designed cooler and is very quiet, and had more than enough grunt for 1080p gaming (it'll even handle most games at 1440p without any issue).
Case: This case, also known as the Enermax Ostrog, was on sale for pretty cheap at my local shop. I was pleasantly impressed. For a $40 case with a window, the build quality and cable management options are pretty good. I find the ventilation holes in the window distracting though (especially since the two of the are different), but it does allow for more fan placement options. It comes with a rear exhaust fan, which I moved to the top so that it would work with natural convection. There would be enough room in this case to install a 240mm radiator at the top for more serious cooling.
Power supply: It's a decent unit with good reviews, 80Plus Bronze rated, and provides plenty of power for this build. The maximum power draw of the system (at the outlet) is 350W while running Prime95 Small FFT and FurMark simultaneously, so it's comfortably within the specs of the PSU. Not a modular unit, but for the price, you can't have it all.
Optical drive: I had one so I put it in. Im starting to doubt the usefulness of having one though.
In all, the system works quite nicely. I've included pictures of some benchmark results. It does well for 1080p games as intended. It's also quieter than I expected, which is a bonus.