Since this came out with the Drowned City, obviously the number one user is Michael McGlen. Spend two bucks, a card, and a play action, and you get a refund on those dollars as long as you find somebody to shoot. Then, spend a resource to do it again twice. With Locked and Loaded, it’s an even better financial proposition: spend $2, earn $1, then earn $2 per reload. But he’s not the only great user.

Rogues are all about actions, and this is a tricky way to get a bonus action for people who want a lot of them. Winnie loves taking tests so she can spend skills. Paired with momentum, this is an easy way to take a potshot, especially with a Pickpocket & Dirty Fighting in play.

This might be the second good gun for Wendy Adams. The Bulldog lets her use agility and succeed. This gun gives her a cheap chance to fail.

It’s also a great flexible card for Ashcan Pete. Instead of always having to give up your upkeep resource to maintain Dark Horse, you can use it flexibly to reload the Luger.

Because you can reload it during off turns, this pistol is extremely flexible. And with investment, it can do strange things. Enchant weapon lets Leo Anderson attack at +9. An excellent sidearm.

The ability to replenish the Luger can be interesting for the cases when you need to spend ammo for an other effect than using the weapon.

Well for now the only use case is Warning Shot I think but a single Luger P08 can be used to activate the Warning Shot that you cycle with The Book of War a few times. It gives you the possibility to repel the enemies you don't want to fight and the Book of war can also cycle tactics you use for clues (Followed, Kicking the Hornet's Nest, ...). And you even have the possibility to play those tactic events as fast actions with Chuck Fergus.

To have all these cards in the same deck, I think your best (only ?) choice is "Skids" O'Toole who is also interested in using Chuck Fergus on Cheap Shot, Slip Away, Breaking and Entering and Pilfer.