Red Tobago Scotch Bonnet? Its the only one I know thats the size you have, I am sure others will chime in.
I grow Tobago Red and Yellow and this is just a guess. Mine get enormous as well
Edit:
If it is a Tobago I can eat a whole pepper that size no sweat, they are around 200k scoville and have a heavy chinense flavor. Its a good sauce or cooking pepper.