I haved loved them ever since I can remember them (Halo 2). I have been told many times that they were in Halo1. I don't remember. But I have loved them ever since I saw Johnson and John in the HEV before Delta Halo.
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ODST's are in Halo: CE, but you won't remember them becuase they wore the same armor as the marines, and didn't have the cool black armor we've come to love today. And yes, same here.