Anna Faris -- Hanging by a Thread Off MASSIVE Cliff

​Anna Faris trusted some flimsy rope with her LIFE earlier this month -- rappelling down an incredibly scary cliff in Mexico ... with a laundry list of her famous buddies, including Michelle Williams.

Anna, Michelle, Anna's husband ("Parks and Recreation" star Chris Pratt) and the entire band Grizzly Bear all went on an 8-hour horseback ride ... then rappelled down a giant mountain ... as part of their Coyote Canyon Adventures trip.