It's not the biggest deal, just one of my pet peeves, but I dislike it when everyone in the group wants to play a rare species. If the world is half humans, quarter dwarves, and most of the rest elves and halflings, then it breaks my immersion when the party that met in a tavern consists of a plasmoid, a tortle, a dhampir, and a warforged.
Usually I play a human, elf or half-elf to balance things out because I know the rest of my group is going to go for rarer, gimmicky, or homebrew species. Sometimes I want to play the gimmicky species or use a homebrew, but I know it won't feel special in my group, so I end up saving that for oneshots. I want to feel special too, dangit!
I'm going to be dming a game soon and I'm rather excited that one of my players actually chose to play a human, and another an elf. Finding joy in the little things, I guess lol.