Was playing Dawnguard, and noticed that I had two "Drain Vitality" Shouts. But the second one was identical to "Marked for Death", but the recharge times were 5, 5, and 12. Has not been fixed by turning off xbox, or reloading. Maybe on another save. I mean, it's a benificial glitch though...

I mentioned this in the "official" bug thread awhile ago, but the OP still hasn't added it to the list. I ran into the same bug upon learning the second Marked for Death word from the DB sanctuary. It's kind of cool, almost spammable due to the recharge time.