SAUCE

Played in a 5 hexhex board. 12 for the first turn. After that a turn is to place two stones, or three if the opponent's biggest group is bigger than the player's (recursively).   Passes are always legal instead of placements.

When the board is full, the recursively-largest connected group wins.

Sample game:

      ___OOO________XXX___
  1.  ..  i5      k3  f4
  2.  o3 l4 f6    h2 h6 k5
  3.  i3 o5 k7    h4 j4 g5
  4.  g7 i7 n6    d2  m7
  5.  n4 e5 l6    c5 l2 d2
  6.  b6  d6      n2 a5 l6
  7.  j6  j8      o7 f8 k9
  8.  h8  g9      b4 m3 m5
  9.  e7  d8      i9 p6 q5
 10.  j2  g3      f2 g1 i1
 11.  k1  e3      c3 m1 e1
 12.  c7 e9 p4    n8 m9

Final Position:

|    abcdefghijklmnopq    
|        x x x o x         1
|       x x x o x x        2
|      x o o o x x o       3
|     x x x x x o o o      4
|    x x o x o x x o x     5
|     o o o x o o o x      6
|      o o o o o x x       7
|       o x o o x x        8
|        o o x x x         9
|    abcdefghijklmnopq
 
Groups sizes:
Os: size 23, 5
Xs: size 23, 9  X wins

Notice the recursive aspect of the goal. This is a quite interesting idea to apply in games where it's not difficult to draw (and we like to avoid draws, of course).