I'm still tinkering with that organic, gridless version of Pente I posted a few moons ago. Here is where the game stands now. It has problems and I am weighing possible solutions.
Stuff You Need
2 or more players
Each player needs fifteen stones, each set a different color
Any play area, like a table or floor
The game begins with one stone for every player placed close to each other on the play area. (See top left.) Play proceeds in turns. On your turn, you may place a stone anywhere on the play area as long as it is touching another stone. (See sequence above, arrows noting new stones.) A stone cannot touch more than two other stones, so long strands start to form.
If a pair of stones of the same color are "sandwiched" between two stones of another color, that pair is removed from the play area. Return those stones to the player of that color. (Above: The red player sandwiches a pair of black stones and returns them to the black player.)
Each strand is worth one point. That point goes to the player who has the most stones in that strand. If two or more players tie for the majority, they share that point. (See above.)
For now, the game ends when one player runs out of stones, but I am willing to consider another endgame condition. Because players take back any stones that get captured, I fear the potential for an endless game. Perhaps captures are simply that. Captures.
Problems and Possible Solutions
I get the feeling that no player will ever put themselves in a position where they could have their stones captured because it will give the capturing player a free point. (A capturing player always ends up with one loose stone on the table, creating a new strand in which he has the majority.) This puts a player who is behind at a permanent disadvantage. Instead, the easiest strategy is to just alternate stones into infinity. Black-White-Black-White-Black and so on.
To remedy this, I considered another action you could take on your turn instead of placing a stone. On your turn, you can remove one of your stones. That effectively splits a strand, which could change the majorities in-play. (See above for an example of Red removing a stone.)
Another option would be to change the scoring system so that the value of a strand is based on the minority of another player's stones. In the example above, this doesn't really help Red very much, but it helps White enough to create a tie. Those two black stones are worth 0 because there are no stones of another color in the same strand.
And lastly, I considered allowing a stone to touch up to three other stones, thus allowing a strand to branch out a bit. However, this led to enough problems that I abandoned it as an option.
So here's where the game is at the moment. It is technically feasible, but it isn't fun yet. That's a frustratingly subjective feeling for someone who tries to be objective and rational as I do. I don't know where the fun is in this game yet. Indeed, there may not be any to be found. I post my notes here so that you might find the kernel of fun. I'm happy to take any of your suggestions in the comments below!