Crokinole - quick to learn
While hosting a birthday party for my 9 year old and 7 of his friends,no had to opportunity to teach several of them crokinole. By first demonstrating the flicking dynamic and showing the goal of hitting the center of the board, they quickly understood what was required to take a turn.
For newer playing, I encourage the use of a 'first in' rule for the opening player. That is, the opening player of a round keeps trying until his/her piece is inside or on the 15 line.
The boys especially like the strike-your-opponent dynamic, and quickly caught the bug. Several adults also got in on the action. Kids vs grow ups and family versus family both make fun doubles matches!