Pixel Dungeon is a traditional yet deep roguelike that is completely free, with pixel-art graphics, and a simple interface.
Pro Hold your device as you like as the game can be played in portrait or landscape
Allowing the user to switch from portrait or landscape makes for an easy way to switch playstyles (one handed, two handed) depending on what device is being used (tablet, phone) as well as what is most comfortable for the user.
Pro A good variation in items allows the player to constantly discover new and exciting ways to tackle the game
Next to the typical selection of buffs, de-buffs, potions (that can be either consumed or thrown), weapons and armor (the latter two have to identified and can carry with them bonuses and curses), there are also less common items like random teleportation scrolls, map reveals, etc.
Pro Has a reasonable amount of strategical depth where the player can easily plan out their next move
The top-down, turn-based nature of the game gives the opportunity to plan out a complex series of moves. This way there is no time constraint, and the player can leisurely strategize what they would like to do next.
Pro Being completely free and open-source means that anyone can try the game in order to see if they like it
No advertisements, no in-game store, and available for free with the source code available on GitHub.
*There is a link in the game where users can donate money to the developer. This of course does not mean you have to, but it is marked as a game with in-app-purchased because of it.
Pro Challenging and fun gameplay that lends itself well to repeat plays
Pixel Dungeon's gameplay is intuitive, allowing for it to be easy to get into. What is great though is that it's also very challenging, quickly making the experience both rewarding and addictive. Just one more game is a thought many will have before actually turning off their device.
Pro Tons of replayability thanks to the randomly generated levels
In true roguelike fashion, levels are randomly generated each time a new game is started. On top of this mechanic, Pixel Dungeon goes one step further by randomizing effects of all items as well, so it's impossible to tell if a dropped item will have a positive or a negative effect based on its sprite representation.
Con Overly random
A lot of people see roguelike design as being based around randomness. It's actually a far more precise set of balances than that. A lot of roguelike developers shy way from "randomly generated content" in favor of the term "procedurally generated content." The reason for this is that a well designed roguelike is well balanced enough that if you lose or win, it's all because of the actions you took.
Pixel Dungeon has a habit of sometimes generating dungeons that are basically impossible and sometimes generating dungeons that are laughably easy.