nVidia's first attempt at a 3D accelerator. Reportedly an extremely weird design, not at all triangle-based. Legend has it that its design was fundamentally incompatible with DirectX, forcing a redesign that later became the nv3 Riva chip. Inspection of the 2D register headers from the nv1 and nv3 drivers in XFree86 3.x shows some design similarities though.
These do still pop up on eBay from time to time. It may be possible to support them in the DRI, but they might not be capable of GL in the usual sense.
A 2D driver was available in XFree86 3.3, but was never ported forward to 4.0.
Some 3D support was available in Windows, but it's not clear if that was an early form of DirectX, or GL, or what.