Each of these quick-start PDFs is designed to introduce a game by providing stripped-down mechanics that give a feel for how the game works. Note that they vary considerably in target audience; some are designed for newcomers to tabletop roleplaying and some are not.
Download a few of these free PDFs, share them with your friends, and look through them so you can get a feel for which genre and style of play might appeal most to your group. If you like the teaser, odds are you'll also enjoy the full version of the game.
If you haven't read the books, you may have heard of the wildly successful Game of Thrones TV series. This 32-page PDF includes the Journey to King's Landing starter scenario, characters for players to use, and enough of the core rules to get a taste of the game.
This is a stripped-down version of Chaosium's Basic Roleplaying, a universal system that can be used to play adventures in any genre. This 48-page PDF includes seven brief scenarios: a swashbuckler, two sci-fi scenarios, a dungeon raid, a bank heist, a WW 2 mission, and a post-apocalypse adventure.
Now in its 7th edition, Call of Cthulhu is arguably the most popular horror RPG of all time. This 48-page PDF contains the game's core mechanics, a 1920s adventure called "The Haunting", character sheets, and an account of how the adventure played out for one gaming group.
Cosmic Patrol is about fast-paced "rockets and rayguns" sci-fi as imagined in the pulp era. The emphasis is squarely on story, and players take turns as Lead Narrator. This 24-page PDF includes characters and everything needed to run The Khan Protocol adventure.
Based on BioWare's Dragon Age: Origins dark fantasy computer game, this 35-page Quickstart Guide contains a highly condensed version of the core rules, a reference sheet, an adventure called An Arl's Ransom, and five pre-generated player characters.
Characters defend transhumanity from horrific threats in this mind-bending game of transhumanism, conspiracy, and horror. This 41-page PDF provides simplified rules, ready characters, and Mind the WMD, a fully detailed starter scenario.
This 50-page gamebook is provided in PDF, ePub, and Mobi formats. FAE is a stand-alone game system suitable for any genre. Note that the publishers make it available under a pay-what-you-like plan, so if you wind up using the game frequently please put a few bucks in their tip jar.
This 32-page "boiled down" PDF provides the core mechanics for this veteran universal system. GURPS is a relatively complex game that is supported by a wide range of genre supplements. This Lite version does not provide a scenario or any pre-generated characters.
Lot5R is a game of medieval fantasy set in the world of Rokugan, which is a cross between feudal Japan and China. This 32-page Quickstart is built around the Legacy of Disaster starter adventure and contains pre-generated characters, spells, and basic system mechanics.
This 16-page PDF includes the Savage Worlds Test Drive rules, a fully detailed modern horror scenario called The Wild Hunt, and printable game aids. Savage Worlds is a universal system with expansions to cover a variety of settings. It emphasizes easy prep and a fast, cinematic style.
A mashup of fantasy and cyberpunk, Shadowrun takes place in a near-future world of intrigue, corporate warfare, and threats of all kinds. The game mixes magic, advanced technology, and fantasy races like elves, orks, and dragons. This 31-page PDF includes pre-made PCs and a straightforward introductory scenario.