Favorite Triwizard Tournament Challenge
My favorite one to read about was the second task with the mermaids. Harry was typical Harry wanting to save everyone, believing they could really die.
The one I'd like to participate in is the maze. Now, I'd hate to see giant spiders (Acromantula) and I definitely would not like an outcome like Harry's, but it does seem the most fun, interesting, and exciting (well, okay, the dragons would be exciting, but I also think it would kill me).