Khartoum (1966). It stars Charlton Heston as Charles "Chinese" Gordon and Lawrence Olivier as Muhammad Ahmed, the Mahdi. The problem I see for many modern viewers will be the pretty terrible blackface worn by Olivier to portray a dark-skinned Sudanese. Personally, I'm less worried about that than I am by Olivier's awful hamminess. I haven't seen it in years, and I'm curious how it holds up.
The second is the blackly comic, Royal Flash (1975), the great Richard Lester's film about George MacDonald Fraser's rogue, Harry Flashman. It stars Malcolm McDowell and Oliver Reed, and it really doesn't get much better than that in the seventies for my money. Scripted by Fraser, it's the only one of the Flashman novels to ever be filmed. I haven't read anyof the books (yet). I remember liking this movie a lot.
Zulu Dawn (1979), a prequel to Zulu (1964). It depicts the victory by Zulu forces under King Cetshwayo at Isandlwana earlier in the same day as the Battle of Rorke's Drift. Again, I remember liking it, but I have no idea how it stands up today.
Finally, a strange film I saw bits and piece of on cable several years ago: The Charge of the Light Brigade (1968). It's filled with all sorts of off-kilter moments and Punch-inspired animation. It's supposed to be both satirical and decently accurate, its script be heavily based on The Reason Why by Cecil Woodham-Smith, a study of the Light Brigade's fatal charge. As I'm about to dive into Trevor Royle's history of the war, Crimea: The Great Crimean War, I'll probably watch this first.