Do you have a user who is complaining about high pings when you're browsing the web or downloading on the same connection?

ifconfig(8) offers the following advice

txqueuelen length

Set the length of the transmit queue of the device. It is useful to set this to small values for slower devices with a high latency (modem links, ISDN) to prevent fast bulk transfers from disturbing inter- active traffic like telnet too much.

So,

ifconfig eth0 txqueuelen 0

will make your interactive traffic (read: Quake 3) much more bearable for your pet gamer.