Recently added a few parts, including:
MSI GTX 950 - Picked up a used one of these for $60, it does the job! It can play Witcher 3 on High settings.
Cryorg C7 - Replaced the stock CPU cooler, and the color really pops.
RGB LED light strip - Picks up all the white in the build and looks great. She likes to use the teal setting.
White Extensions - 24pin mobo and the 6pin to the gpu, helps add more white to the build.
Next steps: Getting her a proper 1080p monitor.
My second build, for my girlfriend who also needed an upgrade at $500 budget.
She loves the color teal, and when we found this case at Fry's (an in-store color exclusive) she had to have it. She just ordered a a mermaid decal to fit on the front panel. Tried to keep the internals mostly black.
No GPU - Haven't purchased a GPU yet, but the onboard graphics of the i5-6600 work great for the main game she plays, World of Warcraft. The plan is to buy her a 480 for Christmas.
i5-6600 - Wanted Skylake, and won't need to overclock. We originally wanted an i5-6500, but they were out of stock at the PC store we went to. Picked this up at a discount.
MSI Mortar - Great mobo, had all the features she needed. The bios is easy to navigate, and she got it for $20 cheaper than I did. I'd originally intended on an ATX board but her budget was pretty tight and this fit the bill.
Kingston HyperX Fury - Pretty much the standard for most black builds.
Western Digital Blue - 1tb for $50 was the best bang for her buck. She can add an SSD in the future if she needs it.
Corsair SPEC-ALPHA - When she saw this color-exclusive case in Fry's she threw it in the cart, and demanded that whatever I build her, it be in this. It was harder to build in than my Corsair Air 240, wire management was a challenge.
EVGA 500w PSU - We wanted a reliable brand at a low cost, but a modular PSU was out of her price range. All in all, the wires were easily stashed away in the unused 3.5 drive bays and behind the main chassis. 500w is plenty for what she has.