I'm a tough guy, nothing scares me. That said, my most heart pounding moment was waiting for a whole player-owned castle to collapse in Ultima Online. Dozens of people were waiting & hiding nearby. All hoping for a piece of the big pie, be it loot stored in the structure, or the extremely valuable land to be available for ownership.
So there I was, waiting along the others right in front of the castle. We were waiting for hours & hours, and we kept checking the sign message to ensure that it was indeed about to fall. Estimating the moment it collapses isn't a hard science, folks usually have to take at least half a day off to patiently wait. The closer we got to the latest possible collapse hour, the more crowdy it got. Soon it became a carnival-like atmosphere, with players wandering around selling wares, several entire guilds came & a few started guild-fight contests. Fools were walking about too, shouting that the castle wasn't going to fall, and that we should all go home. Newbies wearing nothing but pants & orc helms running around the castle like little kids. It bears noting that this occurred in the Trammel facet, where murdering & thieving wasn't possible, and placing brand new houses didn't require a completely empty ground (unlike several years prior).
Then suddenly, it collapsed!! The whole place went wild, with people rushing to grab what they can. There were dozens of heavy chests players could not carry. Who knows what were inside. Thousands of metal ingots? Very valuable especially if they were the rare kind. Magic reagents? Probably not as valuable, not unless it numbered in the tens of thousands each. Rares? These were what most looters were after, as some were absolutely priceless. Could be a basket-fruit, or maybe those crystal-clear jars. Or perhaps it was a one-of-a-server kind rare that never respawned, like a stone pillar, or maybe a horse-drawn cart! Whatever they were after, I was not. I was there for the empty patch of dirt. I wanted to place a 2-story home. Almost immediately after the structure came down, houses of various sizes started popping up, then disappearing! And again, and again! It was some sort of bug, where two or more players placing homes on the same spot would not be able to do so. So it was a race against time! Within 10 seconds, the first successful house was placed. It was a small 1-story home, on the far side of the lot. Guilds started 'cheating' by placing boxes in the empty field, someone forgot to remind them that doesn't work anymore lol! Suddenly wham! A large tower appeared, then disappeared! Caught everyone by surprise, and it lagged most of them, enough for two more homes to be successfully placed! I was frantically trying to put my 2-story home down, but no good! Tried again & again, 4 players were attempting to do the same on my side, but they weren't successful either! I change tactic, and try my luck with a small home instead. Wham! A large blacksmith-home was placed! Then the unthinkable, it started getting so laggy with all the players running about, spamming the screen with words, than I got disconnected!! NOO!
When I returned, it was too late. All available spaces were taken up with brands new homes, and all loot captured. I was left empty-handed, with a sad frowny face, and my heart was racing. Oh well. I moved on to the next plot of land, a small house about to collapse in a quiet corner of the world. It came down after 3-4 days, and I got it. I then decorated it, and then sold it at a huge profit. Ah UO...