Chronological order again.
In this cult favorite, Slater plays the rebel Jason Dead (J.D.) opposite Winona Ryder's Veronica. It did not do so well at the box office but in 2006 was ranked #5 on Entertainment Weekly's 50 Best High School Movies list.
Pump Up the Volume (1990)
Slater plays the character Mark Hunter aka Happy Harry Hardon. A lot like Heathers, it was not a box office hit but is another modern cult classic in my opinion.
True Romance (1993)
This movie was actually written by Quentin Tarantino but was directed by Tony Scott. Not sure why Tarantino didn't direct this one.
Anyway, Slater plays Clarence Worley, a comic book store clerk that meets up with a prostitute on his birthday and ends up marrying her.
The cast of this movie was huuge! Beside Slater you had Patricia Arquette, Michael Rappaport, Dennis Hopper, James Gandolfini (pre-The Sopranos), Gary Oldman, Christopher Walken, Chris Penn, Tom Sizemore, Brad Pitt, Val Kilmer (although you would probably never recognize him), and Samuel L Jackson. Great movie. Great cast.