While we're talking about clever quantizing, we should mention the vertex normal encoding. In MD2 (iirc, not sure about MD1) each vertex normal was stored as a byte which indexed into a pre-established array of unit vectors which were more or less uniformly distributed around a sphere. It was a creative way to have good-enough per-frame normals in a tiny amount of space without forcing the engine to do any painfully slow per-frame normal generation (with the floating point division and square root which that entailed).