Getting my first accessory for my titan was what made me happiest, lv1 uncommon sash-thing. Proudest was having dug up nothing but (good) uncommon armor for lv8, and not even in the crucible. It looked almost as good as I'd hoped. Most frustrating had to be getting the hang of PvP, finding good weapons to drag with me into the crucible and finding my flow. Turns out I'm better with a hand-cannon, shotgun, and machine gun than I was with any other primary weapon in the arenas.