Hmm, this is a tough one
I'll guess Snape
Riddle
Hand me a book,
My badge I will wear,
But try not to overlook
The burden I bare.
(Not sure about the first two lines, although the burden of trying to keep Harry alive for Lily and DD would be difficult)
Orders I'll follow,
Dark wizards I'll fight,
'You keep them safe in Godric's Hollow,
Or well lose them one night.'
(He followed DD's orders and fought against Death Eaters secretly. He also told DD to keep Lily safe in Godric's Hallow)
Old friend's I will lose
Over and over again
Love or opinion I will have to chose,
While the beast I'll have to tame.
(Well, Snape did have friends like Lily and the Malfoys and other DEs. But he couldn't really stay friend's with them being on both sides of the war.Also, he had to chose between Lily and his likeness for dark magic. Not sure about the beast line, though unless it's supposed to reference the beast in him that likes evil things twisted )
Keep an eye on that plot hole,
Please don't let me fall in,
Before Harry takes his stroll,
So the Light side can win.
(Err, plot hole being the Snape can't be all that evil and what not, and Harry taking the stroll is a reference to Harry's "death" in the Forbidden Forest by Voldy, so he can't harm any more people)
Yep, yep, that's my guess. 4laugh
edit: Happy belated B-day to you too, Herms!