N7

From Mass Effect Wiki

'N7' is a vocational code in the Systems Alliance military. The 'N' designates special forces, the 7 refers to the highest level of proficiency. It applies to marines who have graduated from an elite training programme. Both David Anderson and Commander Shepard are classified as N7; Anderson was one of the first graduates.

If Shepard is equipped with any weight of Onyx Armor, the distinctive N7 and red detail on the right arm will be emblazoned on it. According to The Art of Mass Effect, the red detail symbolises the human blood Shepard must sacrifice to stop Saren. The red stripe is also a historical reference to the red stripes commanders wore on early space missions to make them instantly recognisable.

The design is available as a t-shirt from the BioWare website.

The Medal of Valor achievement (completing Mass Effect on Insanity difficulty) unlocks an N7 gamer pic.