Here's my top 10. Each of them was an "oh sh*t" moment.

1. Pong

2. First BBS connection (on a 300bps modem)

3. Mosaic

4. Altavista

5. Napster

6. Gmail

7. Google Maps

8. iPhone 1 (followed by the first homebrew apps, a full year before AppStore launched on iOS)

9. Patreon (ok, this one is not sw related)

10. Bitcoin

Bonus (both sw and hw): Oculus Quest 2. 10x compared to DK2 or other early VR prototypes I tested in the past decade.