Warhammer Fantasy Roleplay
In the grim, dark, grimdark fantasy version of Late Medieval Germany, you will roll up peasants and be slain by fantastical creatures and Daemon lords vastly more powerful than your character can ever hope to become, no matter how much experience he gains. Unless you have the Tome of Corruption supplement, in which case, you can be a badass motherfucking Chaos viking.
Either that, or he'll just die of cholera.
Warhammer Fantasy Roleplay is, as its name implies, a roleplaying game set in the world of Warhammer Fantasy Battles. It has had a checkered past, going through a number of different publishers and frequently sitting for years in development limbo. A 4th edition is currently being developed by Cubicle 7, the pdf being released in August while the physical books being released in December.
Although the setting is occasionally Tolkienesque, it generally takes far more inspiration from the real world, being essentially an alternate universe version of Europe circa the 1500s. This means that firearms are fairly common but also fairly inaccurate. Similarly, magic exists, but it has a chance of raping you with eldritch energy. Humans, as well as their dwarf and elf allies, are opposed by beastmen, orcs, daemons, trolls, and all manner of other horrible things that may inflict loss of life and limb, usually with far darker interpretations than their Dungeons & Dragons counterparts.
Nearly every portion of character creation can be rolled leading to amusing tales of a peasant, a noble, a doctor, and a sailor getting together to claim a lost dwarven stronghold. The best class is ratcatcher, as it has the most important piece of equipment in the game, a small but vicious dog.
The system in general, especially in combat, is extremely (and often hilariously) lethal, and has many rules for crippling injuries and critical hits. This can cause, for example, a lowly badger bite to result in the loss of limbs, and turns attempting to mount a horse into a dangerous endeavour only undertaken by the most foolhardy of warriors.
It is also probably the only high fantasy universe, in which magic is not (terribly) OP. Not so much because the rules don't have spells that can deal 4*1d10+4 damage every hit having a chance to be critical, dealing another 1d10 damage, which keeping in mind that a PC min/maxed and lucky too can at most have 22 hitpoints and 13 damage reduction is quite a bit. No. It's because of the fact casting even a lowly fireball has the chance to open a rift to the realm of chaos that sucks you in so your ass can be eternally fucked by Slaanesh. And for some reason the Lore of Light has more listed healing spells than the Lore of Life.
Perhaps the biggest claim to fame for the system is the extreme amounts of character classes available to players. While the base game is generally rather simple (start as noob wizard, then shit wizard, then ok wizard etc) additional books have added a shocking amount of player choice. Want to be a rat catcher or a slave? How about a Grail Knight or a Vampire? Want to play a warp stone sniffing Skaven or champion of Nurgle? All of these are options. Highly recommended is playing with the Career Companion (even if the book itself is rarer than pieces of the holy cross) since it adds literally hundreds of classes from all the released books, but be aware that some aspects they add (like new types of magic) are not in the book and might require some extra legwork or modulation to figure out.
Editions
Over the years, Warhammer Fantasy Roleplay has had four editions, with much skub over which one is best. The only thing that anyone can seem to agree on is 3rd Edition was shit.
First Edition
Published by Games Workshop themselves in 1986, First Edition is... strange. It was made before a lot of Fantasy's setting had solidified into what we know today, and it shows. Karl Franz is a weak old man who is assassinated part way through one of the modules for example. The game was a gleeful mashup of the Basic Roleplaying System used by Runequest and Call of Cthulhu with AD&D, bringing the dynamics of humans, elfs, dwarves, and halflings into a gritty, dirt covered world where every combat had a good chance of permanently maiming a character. The combination was an instant classic, and Empire In Flames was an iconic introduction to the Old World that would go onto inspire many authors, including William King's Gotrek and Felix series.
Second Edition
Published by Green Ronin in 2004, Second Edition mostly built on the first. It faced the unenviable job of matching the increasingly high fantasy bent world the tabletop game was building with the low power feel of the first editions, not always gracefully but in general it managed. It was notable for adding a number of new careers, including the aforementioned Chaos Champion, Grail Knight, and Vampire paths. The flaws of second edition mostly came down to the era when it was released, where companies were pumping out books quicker and quicker, often with high railroading, which can lead to problems in a system where combat is so lethal. Still, the books for Bretonia, Norsca, Kislev and the Border Princes are generally considered high marks, and you can always play the old modules with the new ruleset. Also the Skaven book, which in addition to letting you play as Skaven in campaigns, also gave some of the most in-depth background to the teeming little ratmen in existence and is a good read for anyone interested their fluff.
The second edition divided the ridiculous large amount of skills into actual skills and talents. Skills existed as Basic Skills, i.e: skills that any character could roll for, even without being trained in the skill, but with a penalty of halving the Characteristic and rounding up, and as Advanced Skills which required the training, no matter what. Talents were in turn, for the most part, advantages that influenced the use of Skills, Characteristics or Actions, either at all times or under special circumstances.
Another thing that the second edition has sorted out positively were Skill Groups by making use of categorization. Skill Groups refered to skills that consisted of "sub-skills", but where each sub-skill counts as a standalone Skill that had to be learned in order to be used without any penalties. Examples of Skill Groups were skills like Common Knowledge: Land X and Common Knowledge: Land Y. Both skills belong to the Common Knowledge skill group but are actually two standalone skills. While not a change in the mechanic itself, the way this is presented in the Corebook allowed both the GM and the players to see through how the system has been built without being overwhelmed by a clusterfuck of 100+ uncategorized skills, like in the first edition. The same method has been applied to Talents, i.e: Talent Groups.
While 1E made use of the standard set of dice (d4, d6, d8, d10 etc) of other popular Roleplaying Games, the second edition made use of two d10 exclusively, incorporating D% in Characteristic and Skill tests, and 1 or 2d10 for damage rolls.
Third Edition, aka the bad one
Published by Fantasy Flight in 2009, having acquired the rights to both WFRP and its sister game Dark Heresy, Third Edition is almost universally reviled by fans. Ditching d% for funky custom dice, tokens, and a pile of cards, Third Edition was more board game than RPG, and the box set (because it never independently released the book) only had enough for three players and the GM. Meanwhile, the story itself was much more heavily weighted toward high fantasy cooperation between Humans, Elves, and Dwarves, generally leaning away from the blood, mud, and shit that had characterized first and second editions, robbing the series of everything that made it special. The game was only active for 3 years before Fantasy Flight declared it dead, and good riddance. That being said, a lot of the ideas from this game and transfer them into the Star Wars Roleplaying Game, which is generally playable. Generally.
Fourth Edition
Published by Cubicle 7 in 2018, 4e is a return to the ideas of first and second edition. D% is back! No cards or tokens! It basically puts us right back where we were in 2004, which could be bad or could be good, hard to tell at this point. The biggest change the system makes is combat. Combat is now a series of opposed skill tests, with damage being dealt if the attacker outdoes the defender in Success Levels, even if both are in the negatives. That means it's possible to hit an enemy AND critically fumble, but also reduces the whiff factor that plagues early levels of a lot of percentile systems. Time will tell if this edition will live up to its predecessors. After months of playing, 4th edition is like second one, I can say fights are fast and positioning is more critical, magic is more consistent, and set of optional rules let GMs to choose how heroic their warhammer will be. Only problem? Cubicle 7 screwed proofreading and there's a lot of errata to take into account. Shooting is overpowered, though.
There was also some amount of controversy over the character artwork, which had things such as a black wandering Merchant and an obese Smuggler. Much polite and calm debate was had over this matter and its place within the Warhammer Fantasy universe.
Because Fourth Edition seems mostly as a way of reliving the glory days of First (and occasionally Second) edition, most of the published materials are translations or rewrites of first or second edition adventures.