My best Hattrick memory was when the city where I lived (L'Aquila, Italy) was hit by an earthquake. I received a lot of support, a lot of help, a lot of love. It was a very hard time and Hattrick was there, with its community, with me. I will never forget that.
What I like about the Hattrick community is that there are real people and you don't just compete against the computers. You play against each other, but you can also help each other in the forum and talk about everything.
The first championship I won is one of my best Hattrick memories. I won the title in the 8th division by scoring a 4-3 winner in the 86th minute of the last league game. This put me tied with two other teams and I clinched the title on goal difference: 62-14 versus 61-14 and 54-11. I'll never forget the player who scored that goal, my Norwegian star striker Olav Aamot.
One reason I play Hattrick is because I like the cyclical nature of the game. You start with an idea about what kind of team you want to build, then you train long-term (up to 3 years in real life!). While you build, you can test and try to comprehend the aspect of the match simulation that you want to master. I also like the tactical choices you have to make for each match. But the most important component is the community.
What I like about the Hattrick community? Everything. I like all the help you can get in the forums about the game, but also for everything else it gives you in everyday life. Hattrick is my favorite social network.
What I like about Hattrick is that there are not 248 925 784 skills that you have to pay attention to. I like that there are several (but not too many) tactics and that they all have weak points that other strategies can beat. I like that this is a slow game, it fits my private life. And that is probably also why I still find it interesting after almost fifteen years.