Really the entire personal computer industry's early success was due to VisiCalc, followed by Lotus 1-2-3. Likewise for WordStar, then WordPerfect. It was the first thing I ever heard referred to in the press as a "killer app", which I think of every time someone here makes the claim that nobody called applications "apps" before the iOS App Store.
Both Lotus 1-2-3 and Symphony remain embedded in my muscle memory.