Two games come to mind.
Game one, we’re at the kitchen table and wrapping game one when another guy drops in. Sure, cool, his commander is
Neheb, the Eternal. Cool, that’s fine, I decide to keep rolling with my 25$ Talrand. his turn one rolls in and we see the
Mana Crypt and
Grim Monolith drop. The rest of the game was fairly inconsequential, I had some sway over the table as “the mono blue deck”, but what ground my gears was the enormous
rift between the power level of thetable and the guy. It was clear a lot of money was in this deck, which I don’t really look down on, but everyone else was 50-200$ neighborhood. I’m mostly to blame, for not asking around for power level, or grabbing a better deck, but everyone was around the same level as each other bar me and him. Now I always ask around for power level before starting play. Lesson learned. But I really doubted if I wanted to play commander again if that was going to be the environment.
Other game was a lot simpler. One of my favorite cards in the game is
Opalescence for the awesome art and game-winning effect. I draw into it and need blockers real bad so I play it down. Only, I had
Enchanted Evening on my board too. So all enchantments are creatures with power/toughness equal to their cmc. And all permanents are enchantments. So, everyone’s lands are enchantments, therefore becoming 0/0 creatures, and die, oops, and I felt really bad for causing mass land destruction in a
chill game. Then we just beat the stuffing out of each other with the rest of our permanents. But I really felt bad. Nobody got mad, but I felt pretty guilty over a card game and didn’t want to play for a bit.