"What RPG do you think is currently being slept upon?"

 I was farnarkling around Reddit and stumbled upon this:

And it attracted by attention. 
Now, I've been playing tabletop RPGs for a number of decades that gave me the heebie jeebies when I started to think about it, and I know that, with one exception, pretty much ALL TTRPGs are flying under the radar and would be regarded as 'niche', but rather than recommend them, I thought I'd go a little deeper and try and dig up some real buried treasure.... 

With that said, I'm going to bring up three games that are criminally underappreciated and deserve more attention. They're games I'd definitely recommend picking up. With that said, instead of playing them 'out of the box',  they feature mechanics, ideas, and settings that definitely need to get more eyes on them.

The first is 'Swashbucklers of the Seven Skies' by Atomic Sock Monkey Press...
...a fantasy-adventure game about swashbuckling sky-pirates!

First up, it has one of the most unique, imaginative and fertile settings imaginable. The setting itself is a hemispherical dome of filled with floating islands and debris, above a weird sea of goop that swallows whatever falls into it. The dome itself is divided into multiple sections by lines of latitude and longitude and has a bizarre series of crazy weather patterns and seasons which has all sorts of impact on navigation, travel and exploration.

Essentially, they've created a sky environment which makes for a setting as exciting as any waterborne fantasy and they've made it fresh and new and exciting. 

The resulting technology is great, fits the flavour of the setting to a 't' and is just some great worldbuilding. They also have sweet rules for shipboard combat, roles, three-dimensional naval battles.

In addition, they have a series of vibrant island civilizations which add beautiful texture to the game which allow almost any different swashbuckling archetype, from burly warriors from the frozen highlands, sly poisoners from the labyrinthine streets, bold musketeers in service of the queen, cackling noblemen, mysterious masters of crime, scimitar wielding desert nomads, etc... AND they've left enough of the world unmapped to leave plenty of places for the GM to make their own modifications and leave some mysterious areas on the map where 'here be dragons'. 

For all this, the while thing is contained within a single, digest-sized book which should be pretty inexpensive to require.

The system itself (PDQ#) is fun, loose and narrative and works something like Fate. Particular highlights include the systems for damage and advancement. However, it would be easy to loot it for the bits that you like and combine them with 7th Sea, D&D, Wildsea, Fantasy AGE, or whatever your preferred system might be.

The second is 'Lace & Steel' by Pauli Kidd.
This Australian-made Swashbuckling Fantasy game has so much to recommend it, I almost don't know where to start...

Almost...

The setting, Mittelmarch, is a fantasy world based extremely loosely on 17th century Europe (c. the English Civil War). Its approach to fantasy owes far more to the folk and fairytales of that time than to modern, post-Tolkien fantasy, with playable races like centaurs, satyrs, pixies, trolls, harpies etc... and a very flavourful magic system which feels much more 'magical' than D&Ds 'Tool-Box' or 'Golf-Bag' approach.

Duelling uses what to my mind is is ONLY great card-based system for combat and includes options for both physical and social combat (reading them to filth!) which captures the feel of 'playing against an opponent' rather than trusting to chance.

It also has one of my favourite systems ever which gives mechanical weight to things that your characters feel passionately about, whether positive (patriotism, freedom, your beautiful fiancee, your word of honour, your family's heirloom sword which has been passed down for generations) or negative (duplicity, fear of heights, Sorcery, that lowlife scoundrel Lord Smedley - damn his black heart! - and foreigners). 

Basically, the way it works is that passions give mechanical bonuses or penalties to succeed, but make the consequences of failure more extreme. Player actions can also have an effect on these passions (a stalwart hero forced to go undercover might initially quail at the idea of such a dishonest, underhanded tactic, but might grow to appreciate its efficiency, for instance, or a hero's ardour for their fiancee might dim as they begin to see them in a new light). Not only is it a great way to inspire role-playing, but a great way to reward a player without giving them another Magical +2 Sword to throw on the pile (Your actions in service of the crown have improved your Connection to the Royal Family, giving you an enhanced bonus if, for instance, you need to request a favour in the future).

The whole thing would work IDEALLY in a game which attempts to duplicate the feel of something like 'The Princess Bride'.

Like 'Swashbucklers of the Seven Skies', this is another one where you can just take bits and marry them to your preferred fantasy game (and I'd probably recommend it). While it's a magnificent game, it WAS created in 1989, and some of its mechanics are a little over-complex and feel a little outdated and in need of a bit of an overhaul. I suspect it would work VERY well with '7th Sea' (again), but even moreso with Green Ronin's 'Blue Rose' RPG.

The third is 'Atomic Robo' based on the comic series by Brian Clevinger and Scott Wegener.

The game uses the Fate System and is about teams of two-fisted action-scientists battling Nazis, Rogue AIs, Giant Radioactive Ants, Invasions from the Vampire Dimension, Dinosaur Mad Scientists, Enormous City-Destroying Atomic Monsters and Weird Perils! 

The game is FUN AS HELL, but suffers from being stuck in a niche so much smaller than it deserves. Basically, if you're not a fan of the comic, or of the Fate System in general, you might not even know the game exists, and even then, would be entirely entitled to overlook it. This would be a mistake, as it contains some of the most AMAZING and USEFUL variants on the (extremely modular and adaptable) Fate system, and almost all of these are easily adaptable to any other game.
Also, the game system itself is just far, FAR more versatile at simulating stories and genres beyond its source material! (Personally, I'm a massive Atomic Robo fan, but I understand that not everyone can possibly be as discerning as me!)

The main system is 'Brainstorming' which is designed to simulate highly trained experts on the cutting edge of science putting their heads together to resolve some inexplicable situation or problem. 

HOWEVER, what is ACTUALLY is is the best dang game mechanic for simulating any sort of investigation or mystery solving, whether it's Columbo, Scooby Doo, Sam Spade, The X-Files, Call of Cthulhu, Batman, Encyclopaedia Brown or anywhere in between.

It elegantly solves every single problem that TTRPGs have had in running mysteries ever!

Simply put, the GM doesn't need to lead the players around by the nose or make sure they put the clues together, because the GM doesn't even need to know the solution. The Players will tell THE GM what the solution is. It's a series of skill checks, using clues gathered throughout the game, in which the players collaborate to assemble the true story of what's actually going on. 

And because the PCs are great detectives or experts in their field, whatever they come up with between themselves is the right answer! Not only does it take a LOT of burden off the GM, but it also allows the Players to feel like great detectives gathering everyone here today to present the facts of the case... rather than frustrated puzzle-solvers trying to read the GMs mind.

There are other systems in there, like the system for creating high-tech inventions, or building, using and maintaining your patron organization, or 'Mission Briefing' system in the Atomic Robo supplement 'Majestic-12', but Brainstorming alone is worth the price of admission and can easily be converted over to any other system.

With that said, the system itself would work extremely well even if you're not using the 'Atomic Robo' setting. It's a great pulpy system that would lend itself beautifully to simulating anything from Mystery (from Sherlock Holmes to Scooby Doo), to Science Fiction (from Pacific Rim to Stargate), to Supernatural Pulp (from The Mummy to Hellboy).

And there ya go. 
Hopefully, this'll attract some interest! Have Fun! 

Anyone have any others they'd like to recommend?