Guild Wars 2 is the MMO that likes to be different. Capped levels and gear progression. Regular story releases. Jumping puzzles. Instant travel. A highly dynamic combat system and classes that change almost entirely depending on weapon choice (two of which you can swap mid-battle). Three-way server wide PvP complete with castles and siege. A small scale PvP that eliminates not just gear, but also level as a factor. Its a unique game with a unique art style. Contrary to many MMOs, you fellow players do not compete with you for resources or kills, so they are always a welcome sight.
The base game is free, with the expansion, Heart of Thorns, being buy to play. And you really can never pay another penny. There is an in game store using Gems, which you can buy for real money or in-game gold. Also, the vast majority of the items in there are purely there to make you look pretty. The only items you might want to splash on are additional bank slots.