What's your favorite kind of antagonist?

Thinking about all the different kinds of antagonists after realizing the last few books I've read didn't have a clear-cut bad guy (or girl). My most recent read was Beauty, by Robin McKinley - a retelling of the Beauty and the Beast story. Usually Beauty's sisters are sniveling, spoiled, antagonistic creatures, but in this version they were given good qualities and are much loved by Beauty. And there's no Gaston in this version, either, so who does that leave for anatagonists?

My very favorite kind of all! - the Beast, who everyone thinks should be the bad guy, but he turns out to be the good guy.

Here's some other "antagonists" I've encountered recently:

• Physical handicaps. In The Window, by Jeanette Ingold, 15 year old Mandy survives a major accident but loses her sight
• Curses (or other dark forces). In A Curse as Dark as Gold, by Elizabeth Bunce, you get three different antagonists - but it's not clear until the very end which is the REAL bad guy or why, exactly, he's out to destroy Charlotte's mill and her family
• Tradition. In Lady in Waiting by Susan Meissner, Lady Jane Grey's main nemesis is the tradition of noble parents arranging the most politically and financially expedient betrothal
• Prejudice. Racism in The Help, by Kathryn Stockett (personified in Miss Hilly!)
• Nature. Surviving a plane crash in the wilderness in Hatchett, by Gary Paulsen
• Inner demons, like addictions or depression.  In Revolution, by Jennifer Donnelly, Andi struggles with guilt, depression and drug abuse, feeling she's to blame for her brother's death.
• War. In Leviathan,  by Scott Westerfeld, the conflict comes from the faceless opposing side. But when two teenagers from the opposing sides meet - you've got another one of those scenarios I love where the bad guys turn out to be the good guys 
• Temptation. In Like Mandarin, by Kirsten Hubbard, Grace befriends a girl with a bad reputation (there are many other subtle "antagonists" going on in this story, too)
• Clash of culture, or values, or ideology: in Esperanza, by Pam Munoz Ryan, the young protagonist has to adjust to a new culture and way of life drastically different than how she was raised
• Institution/government: the Capitol in the Hunger Games series
• Difficulty communicating/misunderstanding: the basis of many literary novels

What's your favorite kind of antagonist, human or otherwise? Which ones did I miss?

Late addition: just found this AMAZING article on antagonists by Kirsten Lamb (via Adventures in Children's Publishing blog) that goes into a lot more detail. A must read!