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The main Sudoku App from Conceptis has some variants such as diagonal, irregular, mega, odd/even ↓
https://play.google.com/store/apps/details?id=com.conceptispuzzles.sudoku
And they have an app with SumSudokus/Killer Sudokus:
https://play.google.com/store/apps/details?id=com.conceptispuzzles.sumsudoku
And Cracking the Cryptic themselves have released two premium apps that focus on one special variant:
https://play.google.com/store/apps/details?id=com.StudioGoya.SandwichSudoku
https://play.google.com/store/apps/details?id=com.StudioGoya.ChessSudoku
Conceptis has a few good ones. They probably play better on tablet, but are phone compatible. The sales model is a couple free packs of puzzles, other packs which you can buy individually (some are tablet-only), and one free puzzle each week (which are available for a month after posting).
Sudoku
Pic-a-Pix (aka Nonograms)
Fill-a-Pix
Cross-a-Pix
They have a much wider variety on their website, and I think on iOS, but this is what's on Android so far.