Hellomyname Keyes

Hellomyname Keyes is an Easter Egg found on Captain Keyes' uniform. You'll find that it says HELLO MY NAME than below it another patch that says KEYES. Due to the lack of the word "is", it has been speculated that Bungie didn't have room to put the "is" in during the production process. On the left of the badge you can see the Marathon symbol.

You can see it using a 2x pistol in the Pillar of Autumn, or a 2x/8x/10x S2 AM sniper rifle in the Truth and Reconciliation, or in Halo Map Tools (more accurate). It can be seen clearly in the cutscene where the Master Chief arrives at the Pillar of Autumn's bridge. To find it in Halo Map tools, go to Bitmap and it's the first one (capn_patches_decal).