This One's for Jenkins!
This One's for Jenkins! is an achievement in Halo: Combat Evolved Anniversary. It is awarded for killing at least 50 Flood combat forms within the level 343 Guilty Spark, on Heroic difficulty or higher. It is represented by an infection form on a Monitor, with "50" above it.
The achievement is worth 10 Gamerpoints.
No particular strategy is necessary, just go through the level and you should be able to get the achievement.
The achievement references Wallace Jenkins, who was infected by an infection form and transitioned into a combat form, though he was able to retain some of his own consciousness, and whose helmet the Chief retrieves the recording introducing him to the Flood from.