Definitely the Quinn-Hynes Demolition Derby and McKenna v. Ryan v. Undecided v. Dillard. Regarding the latter, polling history shows it to be definitely neck and neck, even though Jim Ryan had a substantial lead at the end of last year.
Update: Going to pick McKenna on the assumption that the Rolando Cruz albatross is the most prominent thing voters know about any of the candidates. McKenna is outpolling Dillard + (undecideds break for McKenna over Ryan / Ryan's anti-momentum) = victory. Just my guess.