Although it never made it into production, Bell developed a crew escape system for the two blade AH-1 Cobra. The most unique feature was the main rotor blade separation system. The system pyrotechnically severed only one blade at the cuff, and relied on the resulting rotor imbalance to rip the mast off the gearbox.
Actually, the mast was severed by a second explosive charge. In the film I saw of a test on a rocket sled the severed blade immediately “crashed”, while the blade/hub/mast assembly flew down range toward one of the documenting cameras as a balanced assembly. Funny to see the spectators with that camera run for their lives as the rotor got nearer and eventually flew over them.
The Cobra ejection system did not use seats, but a modified Skyraider “Yankee” system, This system used a rocket to yank a crew member out by a bungee cord. Never went beyond the full scale sled with dummies.