There are a few puzzle types appearing in puzzle competitions that I would like to propose for discussion, because they share some properties with sudoku. I'm not sure if they appeared in puzzle competitions because they were considered as non-sudoku or if they were included as sudoku variations.
http://gp.worldpuzzle.org/
Latin squares are considered by some people as being a sudoku variations. I'm personally happy to see these kind of puzzle in puzzle competitions rather than in sudoku competition.
Potential issues: absence of region.
Source: puzzle GP website: