Bulletproof Vest and Wolfsbane
A certain Andrew Plotkin has suggested on his homepage about "Werewolf" (the game of Mafia under a different name) that one player could be protected against assassination from the beginning of the game. He suggests wolfsbane against werewolves; we would suggest a bulletproof vest against the mafia. One player could randomly be dealt, say, the jack of diamonds, and have a limited version of the power of the archangel-- in other words, only the power to protect himself against the mafia. This may replace or supplement the archangel. We have played several times with a bulletproof vest, with mixed reults. This could lead to tie situations.
Note - We have played frequently with the bulletproof vest, and he has become a regular, although not obligatory, character in our village. There has, in the past, been some confusion over the "tie situation" ending. If only one mafia member and one civilian are left, the mafia win, because the civilian cannot attain a majority to kill during the day and the mafia can kill off the remaining civilian during the night. Note, however, that if you have one mafia member and one bulletproof vest left, the mafia cannot kill during the night, and the bulletproof vest cannot convict during the day. The same thing would happen if you replace the bulletpoof vest in the above analogy with an archangel capable of protecting himself. Generally, archangels don't last as long, though, for a variety of reasons.
Note also that it doesn't behoove the bulletproof vest to come forward immediately-- the mafia will waste one turn on trying to kill the bulletproof vest. If the vest comes forward, the mafia will be able to use this formerly wasted turn to kill a civilian. However, once the mafia have tried to kill the bulletproof vest, it behooves the vest to come forward. If there is only one claimant to being the vest, then the civilians are assured of at least one person whose word can be trusted.
Note, however, that if you combine this variant with the variant of the devil, it is still debatable whether the vest should come forward after a night in which noone was killed-- perhaps the devil will still waste a turn checking the vest out.