Maybe try out Red Stone Online, Ragnarock online, Maple Story Online, and Tibia Online. All of which are F2P and contain lots of grinding capabilities.
On Red Stone Online you don't have to do a single quest if you dont want to and can basically l…
This may not be completely sandbox, but theres definitely no lvl cap and it's F2P. Also there are countless ways to build your characters, which adds a very fun and addictive quality to this game.
Red Stone Online
If you're looking for a unique experience that meets all your requirements perhaps try Red Stone Online. Multiple ways of leveling, lots of fun and addictive looting, plenty of title quests, main quests, dungeon quests, and 100's of ways to build yo…
If I remember correctly Dragonica Online is practically completely dungeon based... as well as Dungeon Fighters Online. Both Have fun qualities and are F2P, but also have cash shops in case you want a deeper experience.
If you like drops give Red Stone a try. Not overly high on the smexy character level though. You find tons of loot in the game though, which is always fun if you wanna take a break from questing and instance dungeons. Grinderiffic ^__^
You love grinding you say!? you want to grind into infinity and beyond you say!? terrific!! ^__^
Grinding and loots for you in recently updated Red Stone, to your hearts content! mwahahahahaaa!! -..ow my mouse finger
-Also note, F2P