I stumbled upon this spoiler. Looks like legal straight flush + DMH decks just got better. Granted, there is a serious caveat with that first trait - but given time to setup - should be easy to play around. This being on-value with Putting the Pieces Together could become a problem… 
There has been a huge amount of chatter on this one over on Facebook. I’ll summarize, and add my own opinion.
So, we have a high risk, HUGE reward card. Naturally this leads many to consider, is the risk to great, can it be mitigated, and is it worth it.
First, discarding a dude if a cheatin’ card is used against you is bad, quit possibly game losing bad. The biggest fear is getting a cheatin’ card played against you for lowball, since there is not much you can do to stop that. If you won previous lowball, and have a quick draw handgun in play, you can prevent your opponent from playing a cheating resolution of they are cheating as well. Henry Moran can do a lot to save your bacon, but that’s not guaranteed. 108 Worldly Desires tends to cheat very infrequently. The Extra Bet, could really help with not cheating in lowball. Also, if your winner of the day, and have Willa in the shootout, you can ace her, and send your dudes home booted before your opponent can play a cheatin’ resolution.
Also to consider are dudes that you don’t plan on keeping in play. Bobo, and Steven Wiles with The Gambler’s Gun are massive threats for only 2 gr and 2 cards. Mortimer Parsons is another interesting dude to put it on, since if he is alone and cheats he will be sent home immediately (with penalties) ending the shootout before resolutions can be played.
This card could be very good with Putting the Pieces Together in a deck that doesn’t cheat very often (like 108 WD)
This card also becomes extremely powerful in bicycle format (or near bicycle standerd). This gun on Mario Crane, and your looking at causing some pain.
Ofc if your opponent sees you playing with Steven+Gambler’s gun, they’re very unlikely to want to face you anyway, so you need to be packing a kill job as well to press the advantage, making it effectively a 3-card combo.
Obviously easier use is in bicycle, or near-bicycle decks, or very loose flush decks. But other options, such as relying on cheap 1-cost draws a tight structure to cause some havoc might also work.
I don’t think this card impoves DMH decks at all. I think it will be played in WD, straight flush decks.
Heh. You are probably right - didn’t really think that part through. Definitely an interesting card though. Also: artwork: looks like this dude was trying to play Ace high. No wonder he (travis?) had to resort to violence.
I really do like this card a lot.
Even the flavor text is awesome 
I do love this card, but another thing to note with the Gamblers Gun: you can go through the huge effort of making a consistently legal draw hand deck, get this out, put it on a good dude, get that dude into the shootout as the shooter, not cheat ever, and still be screwed by cards like Unprepared, Phantom Fingers, Pistol Whip, Mariel Lewis, Soul Blast, and on and on. Say you have a couple of studs, then you can put this on your lesser stud in hopes they will have a tough decision between dealing with the big stud or the lesser stud that has a Gamblers Gun (if they only have answers for one, that is). But if they have no answers for either, you just screwed yourself out of a bigger stud shooter that you could have had.
Putting the Pieces Together, unlike the Gamblers Gun, is a hand rank bump that is nearly impossible to deal with directly - so far the only card that can directly affect it is Hustled. It also is an automatic punishment, rather than depending on the opponent to have a cheatin’ res, so in that way the risks are potentially harsher than Gamblers Gun (minus one or more hand ranks means possibly losing one more more dudes).
I don’t know, just some random ramblings there. I’ve said it once and I’ll say it again - Putting The Pieces Together is the single most complex card to successfully build a deck around, and this Gamblers Gun fits into that vein as well. Love em both!