Eating Cigar
We see Tuco eating a cigar that Blondie has given him while discussing their shares of money. Him eating it is a symbol of Tuco's unpredictability, and it shows Blondie that he may not know who Tuco really is or what he might do in a given situation.
Corn Cobs
We see the Confederate soldier stewing corncobs when Angel Eyes is attempting to get information from him. The corncobs represent the soldiers starving during the Civil War as the Union soldiers had cut off their supplies in order to defeat them by breaking their spirits through keeping them from eating.
Desert
The desert is a symbol of death. It is a place where nothing grows and it is where Tuco takes Blondie. It also symbolizes something about Tuco. That he is willing to go where other men are not in order to get what he wants, which is revenge on Blondie.
Pink Umbrella
While going through the desert with Blondie, Tuco uses a pink umbrella to keep the sun off of him. It becomes a symbol of his cruelty towards Blondie as he doesn't allow him to have any shade for the 100 miles that he's making him walk. It is his way of mocking Blondie on a journey that he knows he is going to die on.
Grave
Just before Carson dies on the wagon, Blondie makes his way to him, and tells Tuco that he has the information about which grave the money is buried in. It's information that Tuco wasn't able to get from Carson before he died. Thus knowing the exact grave is a symbol of Blondie's leverage to stay alive. Without it, Tuco will kill him because he is of neither use nor value to him.
