A long time back I entertained the idea of buying hc.im and using the email address le@hc.im. (my name is michael) Perhaps making business cards with a laser cutout so I could turn the card over if it wasn't apparent. But two-letter im domains are a very expensive ongoing cost so it didn't seem worth it for the gimmick.
I have a very short email address (in the form a@aa.aa) and I haven't found anywhere that doesn't accept it - except for humans, who often refuse to believe it is real and will insist on a longer one.
I have a similar one and it has been rejected many times. I still write to the company but nobody gives a shit. I also tried on twitter.
Surprisingly people are fine with it, I think that this is thanks to social media handlers such as @wazoo - people group all these together as "email and such"
I suppose it should be possible to get an MX record to work with a root domain, but that person that has it would have to probably work for or be the owner.