With insecure low frequency RFID access control badges still in use at businesses around the world and high frequency NFC technology being incorporated into far more consumer products, RFID hacking tools are invaluable for penetration testers and security researchers alike. Software defined radio has revolutionized this field with powerful devices like Proxmark3 and RFIDler available for a modest price. 3D printing has also presented new opportunities for makers to create custom antennas and cases to fit specific tasks. While there is a lot of great information out there about how people use these tools, there is relatively little more than source code available for learning how to develop new firmware to equip these devices with purpose-built logic. This presentation will discuss the overall architecture of the Proxmark3 and RFIDler tools and provide tutorial style examples for enhancing the firmware. Proxmark3 development will be demonstrated by upgrading the stand-alone mode to support NFC operations. For the new kid on the block, RFIDler, we will take a look at how to tweak the system for optimal reliability using 3D printing and enhanced diagnostic tools.