We play a speed game called "Split Second" using math flash cards.
(Note to reader: We play this game on the weekends or during a time when regular homeschooling is not taking place. We also do not mention the word MATH! It is amazing how much fun they have if they do not know they are practicing!)
The games works best if you have more than one player. The dealer deals each student a card one at time, alternating back and forth. Each student is given a few seconds to shout out the correct answer. If the student shouts out the correct answer, he/she gets to keep the card. If he/she calls out the wrong answer, the flash card goes back into the deck. The student with the most cards at the end of the game wins.
When my 6th grader plays against my 1st grader, the 6th grader is given 2 seconds to answer, while the 1st grader is given 3 seconds. It is best to adjust the time so that it is challenging yet not discouraging. We have been playing this game with multiplication flash cards, and my first grader is just spilling out the answers which is so exciting. We were having so much fun, my teenagers couldn't wait to jump in.
You will just be amazed how their competitive spirit comes out, meanwhile sharpening their math skills.
If you have one player, you could try to beat the clock. Set a timer and see how many math facts they get correct within a certain amount of time (like "Mad Minute").
I think this, and your other homeschooling game
Basic graphing and number line math game, are great ideas. Fun, and easily adapted to the child's level of understanding and interest.