This is the first gaming and work PC I've built.
I haven't really built a PC other than in 2002 when I bought a pre assembled motherboard, CPU (I think it was an Athlon XP 1.2GHz) and fan and then went and installed the other parts like a case and hard drive.
The full list parts I used to build this PC is available on PCPartPicker but here is what I went for:
I've always wanted a gaming PC but never had one. Until recently I've played most of my games on consoles but after hearing about Microsoft's Play Anywhere initiative, having already bought loads of games through services like Humble Bundle (I'd buy them planning on getting a PC someday) and wanting to play more games at 60 frames per second I decided to just go for it and build a PC.
Since 2006 I've been mostly a Mac user and I already had a 27" Apple Thunderbolt display so I wanted to keep using that but as the display is Thunderbolt only I had to get a PCIe card that would take a DisplayPort input from a graphics card and send it out via Thunderbolt 2. So I picked up the Asus Thunderbolt 2 Ports PCI Card and selected a matching ASUS motherboard with a Thunderbolt header on it (this didn't work at first and I had to plug my PC into my TV via HDMI and change some BIOS setting to allow Thunderbolt to be on when the PC starts). The Apple display has built in speakers which are OK but I thought I would just use my everyday Sennheiser HD 202 II headphones when gaming.
I also had several old Western Digital Green hard drives that were used inside a Drobo before they were replaced (with larger Western Digital Red hard drives) so I wanted to reuse them for mass local media storage.
The last thing I had laying around was a 480GB SSD I used to use as an external drive for the Xbox One. I'd hardly used the SSD but ended up replacing it with a 960GB SSD so it was just sitting in cupboard.
Once I got all the parts putting it together was pretty easy, everything pretty much snapped into place.
My Windows install is on the Samsung 950 Pro M.2 SSD and the M.2 slot is set to PCIe mode so it's really fast! Booting up takes a few seconds (after all the P.O.S.T stuff). The two Sandisk Ultra II SSDs are in RAID 0 (giving me one 960GB drive in Windows) and hold all my games. The two Western Digital Green 3TB hard drives are in RAID 1 (giving me one 3TB drive in Windows) and is used for local media and document storage. The spare 1.5TB Western Digital Green drive is plugged in to the slower SATA 2 drive and is currently used to hold back ups.
I'm really happy with going for a GTX 1070 as I can play pretty much all my games at 60 frames per second at 1440p on medium to high settings.