Money
We see money laid out on the Sheriff's desk when Virgil is brought in. It is a symbol of the Sheriff's willingness to take what is not his rather than protecting people.
Boot
We see the Sheriff's boot on his desk in the right of frame when he's asking Virgil to tell him how he killed Mr. Colbert. This is a symbol that the Sheriff is ready to squash Tibbs as if he were an ant with all the force of his position and rank.
Squeaky
Gillespie is listening to a squeaky fan in his office as Tibbs is brought in by Sam. The squeaky fan is a symbol of a problem that Gillespie wants fixed and it relates to Gillespie believing Tibbs is a problem that needs to be "fixed."
4:05 to Memphis
Gillespie tells Virgil there is no train at the time of morning he was waiting for one. We hear a train whistle in the background and it is a symbol that Virgil was telling the truth and that Gillespie doesn't know his town as much as he likes for everyone to believe.
Gun
Gillespie tells Virgil that he keeps his town clean so no one gets hurt in it while he's touching his shotguns on the wall. This is a symbol of the threat of violence upon Virgil from the Sheriff and his willingness to harm a black man.
