The question is: RPG that’s easy to use?
The easiest one I’ve used lately has been CAIRN.
Super simple system and, coupled with MAZE RATS, you can throw a whole gaming session together in a very short space of time – create a location, determine interesting features and NPCs, inhabit the land with monsters and quirky goings on (see this video where Baron de Ropp explains the process of using Maze Rats to generate quick material for game sessions). Also the rules booklet is very cheap and extremely short.
The first time I ran Cairn, the player characters were hired by residents of a small mountain village to track down and destroy a mysterious creature, known as ‘the Marching Death’, which had lately begun causing trouble.
This was somewhat of a lie, as the monster had been there for months and had already brutally despatched several other bands of hardy adventurers…still, no point telling the party that and getting them all worried.
A copy of Cairn, some moments ago.