Uses a hidden fixing that is screwed to wall using any small screw you happen to have to hand.
PETG probably best for the fixing itself - it's a tight fit and may break when you try to remove (but only takes a few minutes to print another!).
Shelf designed to support Xbox and 8BitDo (SN30Pro+) controllers but may fit many others - scale as necessary.
Included a fetching multi-material slice too, shown in pics with Eryone Matte Dew White and a variety of sparkly dark colours.
Edit 16Apr22: STL was scaled 10x too big - re-uploaded with correct scale item. 3mf was unaffected / was already correct scale.
The author hasn't provided the model origin yet.