sN3@k33 asks in the HBO forum if anybody has good strategies for keeping Marines alive on Legendary difficulty, especially on 343 Guilty Spark and Assault on the Control Room.

Hikaru-119 came up with a post for the Truth & Reconciliation level and a nice long post about AotCR; it differs from the tactics presented in Evil Otto's legendary walkthrough at Truth & Reconciliation. But it's a lot closer to the tactics I've seen and used myself. Going for that Warthog right away isn't always the best idea.