I've just realized how many of my top 100, especially the top 20, are essentially about marriage. But I'll go with George and Martha from Who's Afraid of Virginia Woolf? just for the fireworks.
Other films from my top list that revolve around marriage:
1. Scenes From a Marriage (1973, Ingmar Bergman)
2. Mahanagar (1963, Satyajit Ray)
5. A Woman Under the Influence (1974, John Cassavetes)
10. Charulata (1964, Satyajit Ray)
15. The Shining (1980, Stanley Kubrick)
16. Jules and Jim (1962, Francois Truffaut)
48. The Vertical Ray of the Sun (2000, Anh Hung Tran)
68. I Fidanzati (1963, Ermanno Olmi)
77. Sita Sings the Blues (2008, Nina Paley)
84. Three Colors: Blue (1993, Krzysztof Kieslowski)
92. Shame (1968, Ingmar Bergman)
95. Drowning by Numbers (1988, Peter Greenaway)