Leo Atreides has a Kickstarter campaign up and running for rollable 4-sided dice.
From the campaign:
d4 dice have a different game logic playout compared to d6. In the game in the picture a pair of d6 would have a play move max of 12, that makes the game tree too unpredictable and makes it hard for the player to plan and make their play. A pair of d4s reduce the max to 8 so the movement is not too complicated and the rate of doubles is 1:4 as opposed to 1:6 which introduces new design options.