Pen and paper games: rules and printable sheets

Games that need nothing but a pencil: tic-tac-toe, dots and boxes, hangman, battleship, Sim and Sprouts, with sheets to print for each.

Questions

Which pen and paper games work for travel?

Dots and boxes, hangman and tic-tac-toe fit on one sheet and need no table. Battleship works in a car with a clipboard each.