In your experience, which are the most common/popular sudoku variants? Note that I'm NOT asking for your personal favorites.
In my view, gattai (2-144+ overlapping puzzles) are not variants as much as they are puzzle extensions. (Clueless Special is an extension of vanilla sudoku, and Clueless Explosion is an extension of center-dot.) There are also hybrids of two or more variants; we'll exclude those for now. I've also excluded those that combine arithmetic with sudoku (such as killer, kakuro, etc.).
Here are the ones I've run across so far. Am I missing any? I've tried to group them in a logical fashion. Many are subsets of others (for instance, x/diagonal, windoku, asterisk, center-dot, etc. are all specific types of the extra-groups variant, many variations in addition to those below, such as
Snake,
Girandola,
Old Lace, etc.). I've included as separate categories only those subsets that I've found in more than one place.
Extra Groups
ArgyleAsterisk
Bold-XCenter-Dot
Clover
Disjoint Groups (LOTS of variations/color patterns in this category)
SnowflakeSudoku-X (diagonal)
Windoku
Jigsaw
No-Box
Plum (No-Box with color groups)
Sukaku
Consecutive
Even-Odd
Greater-Than
Non-consecutive
Chess Moves
Other Box Sizes (such as 16x16, 12x12, etc.)