elizabeth was also contemplating taking a nosedive several times during the jason mcquire blackmail plot.someone always showed up and prevented it from actually happening.
I recall Phillip Todd inadvertently going over the edge after attacking the loathsome Jeb Hawkes, who, ironically enough, later went over the edge himself after Sky Rumson wrestled with him on the precipice, near the conclusion of the Leviathoan storyline.
[spoiler]Joanna's ghost forced Samantha off Widows' Hill in 1840. I'm not sure if Samantha originally pushed Joanna from this cliff or another one.[/spoiler]