There are several sets of rules with this name.
Rorke's Drift[]
These rules are very simple (just two pages), but the game is a real kick in the pants.
It's not especially true to history -- the British, if they win, can expect to suffer 60 to 80% casualties -- but the author guarantees carnage galore and a good time for everyone.
http://web.archive.org/web/20020811230848/http://home.attbi.com/~tsrstevew/RorkDrft/zulu.htm
Rorke's Drift[]
Suitable for any figure scale from 2mm upwards and where either side can win. Specifically designed for a scaled battle of Rorke's Drift where 4,000 Zulus attacked the missionary station defended by 140 British troops on 22nd January 1879.
http://petesweb.zxq.net/ageofmusket/rorkesdrift/
Rorke's Drift[]
1 page rules for the refight of this famous battle.
http://www.gettysburggamers.com/RD.pdf
Rorke's Drift - It's Jolly Deadly, Old Boy[]
A set of rules for 15mm figures. This game is a simulation of that action. The Zulu player can make three assaults upon the British defenses with all of his figures. The British player must defend against these attacks without any replacements.