This mini-expansion isn't in print right now, but look out for it... it's a great set of rule-changing tweaks. Essentially, some basic rule of the game is altered or ignored every turn, even allowing players to come back from the dead for one round (a great touch, when player elimination is one of Bang!'s harder selling points). Definitely worth the few dollars they charge!
High Noon is a very well thought-out little expansion to Bang! It includes 12 cards that are used as meta-effects so that each round the effects of one of them applies. This adds a lot of variety to the base game and it is also used to address some of the issues some people have had with it (e.g. making it a bit faster to play and giving eliminated players something to do too). All in all, it is a must have for any fan of the original.
Excellent addition to the Bang! card game. It changes the mode of difficulty by making the game a bit easier, at times, or more challenging and more fun. Its best, just to get this at the same time as getting the Base Deck. You'll be glad you did.