Justin Theroux showed off his toned physique and good looks while filming his ALS ice bucket challenge video [1] on Saturday. As a pal waited to pour water all over Justin's tight t-shirt and flattering jeans, the actor nominated a special A-lister to get her hair wet: his fiancée, Jennifer Aniston [2]! While we wait to see if Jennifer joins the long list of celebrities who have embraced the ice bucket challenge [3], check out the other stars who have not yet taken the plunge [4].