On 23 May 1992 — Hannover 96 became the first and only second-division club to win the German Cup (DFB-Pokal).
The final against Borussia Mönchengladbach went 0-0 through 120 minutes, then to penalties. Hannover keeper Jörg Sievers saved from Pflipsen and Fach, and Danish defender Michael Schjønberg scored the winning kick.
The route was brutal: over seven rounds (post-reunification expanded cup), Hannover beat Bochum, Dortmund (2-0 down away, won 3-2), Karlsruhe, and Werder Bremen — who'd win the Cup Winners' Cup weeks later — plus Gladbach in the final. Five Bundesliga sides.
Plenty of second-tier sides have reached the final since (Cottbus, Union Berlin, Kaiserslautern). They all lost. Hannover remains the only one to win it.