A game I love is Magic: the Gathering. One of the mechanics I enjoy the most is deck building. There are tens of thousands of cards to choose from spanning decades. Each deck you make is therefore highly personalized and allows for a large sense of self expression. The card pool additionally allows for a huge amount of variation and replayability. Since each game has four players, and each player has a very personalized deck of 100 different cards, games pretty much never play out the same way.
Another mechanic that makes the game what it is is the “lands” mechanic, which is heavily tied in to the game’s flavor. Imagine you are a powerful spellcaster (in this case, a witch, with a small hut in a forest). Each day, to cast spells, you explore the forest, looking for ingredients to put into your brew. You steadily learn more about the forest you live in, getting power from the different locations around you. Each player in MTG is a spellcaster that draws power from the terrain around them, represented by land cards. For instance, you might play mountain cards, or swamp cards. These lands allow you to draw different types of power that do different things. And each player gets more and more land as the game continues, giving them more and more power, so that by the late game they are doing world-shaking things, but during the early game they might simply be summoning small minions. This allows for a sense of progression that makes magic games interesting and flavorful.