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Update (2/7/2015): By popular demand, I've opened the vent holes for those who are overclocking (and possibly using the Pi 2). The cart lid has also been fixed to add more support around the connectors.

This is an NES-styled case for the Raspberry Pi B+ and Raspberry Pi 2 Model B. It is inspired by http://www.thingiverse.com/thing:307832 but is a complete re-design from scratch as it only worked with the Raspberry Pi B.

USB/Ethernet are mounted in front and MicroSD card is out the back.
The case is held together with 4x #4-40 1" machine screws.

Complete parts list (with links to Amazon.com):

Raspberry Pi 3 (Recommended)
Sandisk 64GB MicroSD Card
MicroUSB charger for Raspberry Pi 3
Note: These are the parts I used and are guaranteed to fit. Others will probably work too.

RetroPie (Emulators)

About Retro Pie
RetroPie SD Card Images

Wired Controllers:

USB Controller 5-pack (N64 SNES PS2 NES Sega)
Xbox 360 Wired Controller
NES
SNES
Genesis/Megadrive
N64
NeoGeo
Atari 2600

Wireless Controllers:

Xbox 360 Wireless Controller
Xbox 360 Wireless receiver
PlayStation 3 Dualshock 3
8Bitdo NES30 Pro
8Bitdo SNES30 Pro

PLA@215 ABS@230
15% Infill
90/120mm speed