DescentBB

For me it was the very important lesson of "it's not the length of the missile, it's the size of the warhead"

It's taught me to be "Not too coward, not too reckless"

Problems in video games are like nails, the solution is always "bring a bigger hammer".

Maybe too many to count, but Descent being the first PVP-capable game I played against real people, the most significant ones were what it takes to win in a competitive game. There are the raw skills - can you aim, can you dodge a homing missile - and being able to learn them well enough that you don't freeze up when you have to use them unexpectedly. Being able to do multiple things at once - seeing and evading incoming fire while tracking what your opponents are doing next. Learning what sorts of things work to "catch" someone - the shots that are hard to dodge, missile tricks, all that kind of stuff - and of course being able to execute with the right timing. Figuring out how to escape a vulnerable position and get to a strong one. Guessing what people are likely to do - part of it "what do people USUALLY do in this situation" and part of it trying to learn the habits of individual players. And then there's the heavy mind-game stuff - trying to trick people, predict them, figure out when they're onto you and turning the tables, all that sort of thing.

It's a very complex field, and interestingly, it's not just Descent that this stuff applies to. Much of it applies to other games as well, especially action games, and sometimes even real-life sports.