The first link above leads to the Hammercalled quick-start on DriveThruRPG, and the second leads to the rules reference on Dropbox. Both are free.
With that said, I have a hard time narrowing it down, so I'll choose five below the break. I'm a rebel, and you can't make me do just one. There's no particular significance to the order, other than what I've been thinking about most recently.
Also, all the links to DriveThruRPG in this article are affiliate links. The products may be available elsewhere, sometimes cheaper, but I'm lazy and like DriveThruRPG.
(questions and image from autocratik.blogspot.com)
Symbaroum
Dark fantasy with a ruleset that I can only describe as high-octane D&D. It's a major inspiration to Hammercalled and I like it so much that I own it in two languages (in print, no less). It's also not a direct d20 system descendant, like 13th Age below, so it feels very different from D&D.
Basically, it puts a lot more of the emphasis on the players and what they're doing and less on the GM and their affairs, is far less roll-based, and characters are a lot more fluid. There's no dramatic level scaling, so characters don't ever reach a point where they are invulnerable to lesser challenges, but there's still a meaningful crunch and progression. It's incredibly easy to play compared to many other games, but you don't feel like you're missing stuff, especially if you use the player's guide, which has a ton of additional content.
It's also beautifully illustrated, with an incredible production value.
Symbaroum cover from DriveThruRPG
Degenesis [Site potentially NSFW]
Degenesis bills itself as "primal punk", and achieves this aesthetic perfectly. I think it is a particularly great game. It's made by a concept art studio, and is definitely in the running for most beautifully illustrated RPG in my books (alongside Symbaroum and Legend of the Five Rings).
I don't think that Degenesis is necessarily the best designed game, but it's definitely functional. While there are some minor hiccups, and I run a fair amount of homebrew at my table (which you can find over on the Degenesis official forums or Discord channel, which I run), it generally feels like a refined version of the more recent Shadowrun games as far as how it plays.
I think I've also talked about the various mechanics in Degenesis that I love so much that people have stopped listening to me talk about them, but it does a good job of mixing freely built point-buy character creation with ties to the universe and factions within it.
It has two trailers on YouTube you can check out, too!
Spire
Spire is another punk game, but it's very surreal. Players take on the role of drow in an ancient city-tower dominated by high elves. With strong racial undertones it may not be suitable for all groups, but it is a game where the various tragedies that make up the setting can be played straight or for bleak humor.
The illustrations and interior work are incredible (you'll notice that as a common trend for these first three picks), but it is the writing that really elevates it to the point of being worthy. With a solidly crafted system of small dice pools, the game really flows well both mechanically and as a storytelling device. Actions have consequences, and in the dark intrigues of Spire you will find that the a small action can bring about a massive reaction.
If you're looking for a comparison to other media, you can find everything from 1984 to Brazil in Spire, and it's fantastic. I liken it to Paranoia sometimes when comparing it to other tabletop RPGs, though I'm not sure that does it justice.
Spire cover from DriveThruRPG
Twilight: 2000
Alright, I know, it's not exactly a small name in tabletop roleplaying, since it is a semi-companion to GDW's venerable Traveller family, but Twilight: 2000 is a fantastic game that deserves more attention in the modern day, though its Cold War turned hot setting may not necessarily resonate with the modern audience (or, perhaps, it would be even more poignant given the current state of world affairs).
I think that a lot of people have gotten used to games that feel and taste a lot like D&D, and it's causing some stagnation both in terms of what people expect and how they play and design games. Twilight: 2000 is interesting because I think it's a case where the system is incredibly ambivalent to your characters versus the rest of the universe, and that almost makes it more significant.
I've never wanted my characters to survive more than I have when playing Twilight: 2000, and that's precisely because I knew that their lives depended on my decisions. A lot of games punish you for errors, but Twilight: 2000 demands that you figure out what you're doing and get it done right. The costs for failure are high.
13th Age
Another not particularly obscure title, but one that I think is interesting. 13th Age is for me one of the best d20 implementations out there, and it does a lot of things right.
To start, it gives a strong reason for players to do things through its Icon system, which means that the players are always part of the unfolding action because they can't escape it (cue evil GM laughter), but it also does some interesting things.
Combat, gear, and skill tracking are all done in a way that attempts to minimize the time you waste on such things. An escalation die means that combat naturally becomes more lethal over time, with baddies using their special attacks as it increases (which, by the way, is a great balancing feature that you don't get in default D&D) but PCs getting a flat increasing bonus as it goes up.
It's been inspiring for Hammercalled because not only do the designers do a great job of explaining their decisions, but they also look at some of the paradigms and challenge them. In particular, they're really big on rules being empowering, rather than limiting, which their more fluid approach to many of the systems that were rigid in older versions of D&D permits.
13th Age cover from DriveThruRPG
