most prominent example: 3DFX's Glide API:
http://en.wikipedia.org/wiki/Glide_API
Quake was not OpenGL compliant when it was released (neither was Raven Software's spin-off Hexen II) - OpenGL support came a year later with GLQuake, and was mostly fueled by acceptance of 3DFX's Glide API (of which it was also compliant).
Quake II, Quake III and Quake IV, though, ran via OpenGL (as did Doom3, Heretic II, Prey, and some other titles). In regards to Quake II, the biggest driving force again was not OpenGL itself, but 3DFX's Glide API.
Although ID Software (and partner company Raven Software) have been some of the largest supportive software developers that utilize OpenGL . . . OpenGL as we know it today, in regards to it's highly competitive visual capabilities and also it's performance abilities, owes a lot to 3DFX's pioneering of the Glide API - which was fully based off of the OpenGL API at the time, but was tweaked and targeted specifically for performance. The number of rendering calls were trimmed back to the extent that the API could be implimented solely via hardware, which allowed for games to be able to run extensively faster with Glide than with OpenGL (or DirectX). The performance margin in Glide, as well as OpenGL, was such that the early VooDoo series (through VooDoo3) have become legendary in the 3D graphics market. The Glide API brought new and fresh attention to OpenGL as well, with many new software developers taking a fresh look at OpenGL over DirectX . . . the newfound attention helped the API grow and evolve, and lead to substantial improvements with the API for OpenGl 2.0 released in 2006. The performance increasesand rendering tweaks from the Glide API were even visible for years after 3DFX's downfall and acquisition by nVidia . . . after nVidia acquired the company (and their intellectual property) in 2000, nVidia cards were notorious for outperforming ATI's cards in OpenGL applications through the X1900 series and early HD2000 series.