Either when you were a noob or had no idea it was good. My biggest regret is praetorian foil.. Edit 1: with almost 100 replies, the biggest regrets seem to be LDR and the longbow. Thank God I have mine still. Edit 2: almost 250 replies, I didn't think this would blow up! It's still all exotics or vanilla guns that had good perks. I feel your pain guardians