We have two label printers in G1.
Handheld label printer
Brother P-Touch 2730
Horizontal label tape: Brother TZe-231 12mm tape cassette (thicker tape is supported but this is the standard size)
Continuous feed labels
The panel inside the door in G1 can be used to print labels with your username on them, to identify your stuff in the fridge or tell people not to hack it.
Web interface (including URL to QR code)
Vertical label tape: Brother DK-22205 62mm continuous paper label roll