Word Square - Sudoku, but with letters and words.
SudoKoi - Your next favorite pastime, like Sudoku
Pako - Car Chase Simulator - Arcade game about high speed police chases
UsDoku - Play real-time multiplayer Sudoku.
Pro:Sudoku - Play Sudoku with Apple Pencil on iPad
Sudoku Kings! - Minimalist sudoku experience with competitive leaderboards.