The Bloody Baron
Reasoning: This card symbolizes an straightforward, no-nonsense, experienced person who is difficult to fool. This is a little bit of a stretch for the Bloody Baron for me, since he is silent and shrouded in mystery, which doesn't really fit the 'humerous', 'witty' and 'honest' part of the card... but he does seem experienced and astute, and definitely doesn't tolerate nonesense (look at his 'putting his foot down' on Peeves attending the Sorting Ceremony).
In a traditional tarot deck, this is the Queen of Swords.
Notes
I've always had a fairly clear vision of the Bloody Baron in my head.... I don't know if his costuming is even remotely accurate for a baron, but it's just what I pictured. Overall this was a fairly straightforward card to draw, and coloring it was fun. :)