En Garde was published at around the same time as D & D. I think it ties with Tunnels & Trolls as the second role-playing game published.
Its take on role-playing was VERY different from D & D and its ilk. There was no GM. The game was set in 17th century Paris. Your objective was to climb up the social ladder of Paris.
As I mentioned before, there was no GM. So the game was kind of competitive. You basically planned out what you would do in each week of a given month. The stuff you could do was go to a social club, go to a bawdyhosue, woo a woman, practice your fencing, etc. A lot of the stuff your character did was centered around trying to increase your social level, i.e. going to a club and spending a ton of money on drinks, joining a prestigious regiment, winning duels, hanging around your social betters, etc. Taking a step back, the game is kind of like a caricature of high-school (I'm kind of surprised that noone developed a high-school version of En Garde given the variants that have popped up).
The combat system for duels was pretty involved - you basically planned out your moves and they were cross-referenced to come up with a result. For example, if you lunged at the same time that your opponent parried, your attack missed...but if he did something else, you'd skewer him and inflict damage. Differences in character skill were incorporated into the system by giving the more skilled character extra attacks.
The engine of the game was a series of tables where you resolved your actions via die/dice roll. There was no unified mechanism (not surprising considering how old the game is).
Most attributes (strength, constitution and fencing expertise) were rolled on 3d6 but others (like military ability - the ability to lead troops) was rolled on 1d6. Some actions were resolved by rolling 2d6. Others were resolved by rolling 1d6.
The game was kind of obscure but gained popularity with the advent of the internet when it became possible to have games with 20+ characters running around Paris.
Variants based on Barsoom, Dune, the Royal Navy in 16th century England and Feudal Japan have been developed.