Prof. Scarlet Leslie-Lewis

I take guard from Mia. I quickly rush up to Madam Pince and show her a book that has been damaged. Uh oh... The nearby boy's bathroom is flooding...

Pius Thicknesse because he seems both more decisive and more agile than Cornelius Fudge. Horace Slughorn or Gilderoy Lockhart?

I take guard from Mia and quickly cast a Freezing Charm. I conjure a jar to transport the pixie elsewhere. Watch out for that Fanged Frisbee!

Dobby! Dobby would take the battle seriously, whereas Kreacher likely wouldn't care (unless he had to defend Regulus's honor). Ginny Weasley or Fleur Delacour?

I take guard from Carrie. I attempt to whistle, but realize I could never whistle. I summon a harmonica and play it until Fluffy goes to sleep. There's an Auror around the corner.

Yaxley would likely accidentally set off one of the random objects that Xenophilius Lovegood happens to be carrying on him, allowing Mr. Lovegood to take advantage and win. Alicia Spinnet or Katie Bell?

I take guard from Charlie and send a whoosh of air down the corridor, knocking a student to his feet and his Invisibility Cloak flying. He quickly gets up to chase after his prized possession. It looks like a Bludger is barreling toward the common room!