Nothing gives me more adrenaline than playing a bullet tournament where you can be wiped out in that match for a single move or because you took two seconds to make a move.
Plus, it's the game mode where you can try out all the tactics and openings you've learned in training fairly quickly and without wasting time thinking or waiting for players to play what you want.
But these tournaments are quite spicy. Most players, even though their ratings might suggest they don't play much, actually do and can be quite mischievous. I've played players in the 1400s who are quite good.
There's no time to relax because most of these games will always end with a time crunch. You understand that if you don't finish off the player, they'll play to the end even if they have three or four pieces less. I've had many of these games where it seemed like I was winning, but the opponent wouldn't give up, and I ended up losing on time.
It's quite dynamic. It makes you develop a tactical move or simply see the tactics very quickly, since time is of the essence, and even a second lost in calculating a move can have an impact on the end of the game.
Here are some of the best games. I warn you that there isn't much analytical rigor because they are bullet chess games, so I won't be too hard on myself about any of these games.