The first time I played Quake multiplayer was over modem with my neighbor. His dad had one of those USRobotics V.everything modems and I had a USR Sportster 28k. They negotiated some proprietary protocol like v42 because we had a 140k connect. It was insane at the time.
I vaguely recall that there was a "shotgun" set of modems you could pair up and get 128k over two 56k connections. I had just the one, but it felt so, so good to get sub-200 ping in Action Quake 2 and CS.
I remember a trick of connecting at a standard speed and then running a certain AT command that reduced the latency considerably - from 250ms down to 180 or so. Can't remember what it was but it made a very big difference to Quakeworld. The client prediction made it very playable on a sub-200 ping.