The shortest answer is that it depends on the round being used. Without getting technical, the best bet that's common is going to be 12 gauge, 00 buckshot to the T zone. Chances of survival would be astronomically low with any shot placement to the T zone. Barrel in mouth aiming towards anywhere between 12 o'clock to 3 o'clock (imagine a clock face on a side profile) would do as well, if not better. Closed casket for sure.