Eludiac has suggested adding a "Return fire" or "counter" rule. The idea is that each player can equip two gun cards. The first gun card is your primary range for shooting and the second for your counter range. When you are attacked, if the attacker is within the range of your counter weapon, you may "draw!" If the card's suit matches the suit of your weapon, then you fire a BANG! back at the player whom attacked you. To distinguish between the primary and counter weapons, he suggests placing the primary on top of the counter, so just the counter weapon's range shows.
Later, Eludiac suggests a different variant on this rule. If you play a Missed! that has the same suit as your 1 weapon, then you can counter your attacker. He feels this is simpler as it eliminates the two weapon equipment.
I think this is an interesting variant on the game. I actually made a custom card, "Evade," that allows you to not only avoid an attack, but also bang your attacker. Of course, Evade adds a Missed! to the counter, but it is a similar idea. Eludiac's variation allows you to enjoy the counter without having to add new cards to the deck. As for critiquing his rules, I think there is some problems with his suggestions. First, the suit conjunction. Missed! and Gun cards' suits actually don't align that well, and it looks like he forgot to check this component. I don't think this is going to work. I don't like the "draw!" suggestion either. Too many "draw!" can really eat up cards in the game and make John Pain OP if one is not careful. Especially when the "draw!" unnecessary.
Personally, I like the two gun idea, as it is annoying to just have to discard these cards. I would have your primary gun card to the left of your character card, and the counter card to the right of your character card to distinguish them. Instead of "draw!", or having a Missed! activate the counter, I would require them to discard a BANG! to counter. A Missed! would have to be played in addition to avoid the attack. This makes it useful to have two gun cards, and you can imagine cat balouing the counter gun before attacking a player. I don't think it makes the counter character OP, as he is still having to discard BANG! to counter. As for gun card replacement, you could or might not allow swapping of guns. On each player's turn you might allow them to rearrange their primary and counter gun cards until their next turn. Or you could make them locked in their places until you replace them with a gun card from your hand. I could see it going either way. Anyway, this could create some interesting game play, and I think it is worth considering. Thoughts?