I play cis males only, but not as a rule. I just generally will make male characters, likely in part to feeling better prepared at interpreting them, and in part that I feel like I would not play another gender correctly. I understand that it is an illusion, as I could simply play them as any other human/non-human being, especially as I've played other species without issue. But I feel like I would not be able to give them the nuance and characteristics they deserve, and would end up defaulting to cis male attitudes.
I also tend to want to play old characters, as I feel like young ones are too boring. They tend to have too short of a history to have an interesting identity and lore behind them, and I love the idea of facing large challenges later in life while struggling with the decisions of the past and our own will to change. I played in a one-shot where I made an old farm veterinarian that would roam the lands helping people with their animals, who had a fall-off with one of his sons for joining the army of an oppressive despot, and a merchant daughter that traded in stolen artifacts. Rumour had it my character had killed his own wife, and in reality what had happened was that he poisoned her because she was sick and suffering but the religious fanatics did not want to let her die while she suffered. I love characters with personality problems, dense pasts, and a complicated family.
Does Wilfred count?
Nowadays it is Dropout's Game Changer and Make Some Noise