Indiana Jones and the Temple of Doom
Definitely the weakest of the first three movies (I haven't seen the fourth one), partly cos he's saddled with a cheesy child sidekick and an incredibly shrill love interest, but mainly owing to the careless use of Indian and Chinese stereotypes. They seemed much more comfortable with the French and German stereotypes in the other two movies.
It's still a great romp, with some marvellous set-pieces, especially the high-kicking Chinese nightclub opening, the chase through the mine on fragile carts, and the rope bridge finale. More recent Hollywood action movies don't match this standard, sadly.