Adaptation Displacement: The film is much better known that the original play. It's not particularly surprising given the differences in the medium, the all-star cast and the general improvements Mamet made in the film.
Crosses the Line Twice: The constant berating is nothing if not unique, which makes some of the insults stinging and hilarious, such as Roma's disdain for an Indian client, stating that he was so stubborn, not even the Indian gods could get him to sign a deal.
Levene tries to provoke one of these at the end when, inspired by Roma's speech above, he finally stands up to Williamson, but it's ultimately subverted: in his eagerness, he lets slip something that gives him away as the person who robbed the office the previous night. Williamson picks up on it and spitefully uses it to destroy him.
Ho Yay: Roma's seduction of a customer isn't subtle.
How the Mighty Have Fallen: Levene is said to actually be a pretty good salesman who's currently stuck on a bad streak. You can see how he actually is a jerkass under that sorry exterior as soon as he thinks he's back on a roll.
Shelly "The Machine" Levene. In spite of the way we can see how sleazy he is by his sales tactics, he's such a sad-sack with a sob-story that we can't help but feel sorry for him.
Roma and Moss probably also count since the former gets screwed out of a $6,000 deal thanks to Williamson and the latter gets implicated in the robbery by Levene.
Jerkass Has a Point: Levene's comment to Blake on the leads being too weak to fulfill. When he closes a big deal that boosts his confidence once again, Williamson shoots him down at the end by telling Levene that the lead was a dud and Williamsom had known for months. Which means for all their complaining, the main characters were right about being held back by bad leads.
Magnificent Bastard: Ricky Roma, who artfully manipulates a potential customer while riding his hot streak.
Misaimed Fandom: Not only is the film loved by the very Salesmen it sets out to destroy, but Blake's scene (which is intended as characterizing pretty much everything wrong with corporate America) is used as a motivational tool in workplaces. Of particular note is a Cracked.com article (see Memetic Mutation above) where the author pretty much uses the scene to describe how one might become a "better person", when David Mamet has openly said he intended that scene to show what was wrong with rampant capitalism and cutthroat sales tactics.
One-Scene Wonder: Blake's scene in which he completely berates the office staff for their failure to perform. Especially notable as it's original to the film adaptation.