Divide students into groups of two and instruct them to play a practice game of Go Fish so that they can get reacquainted with the rules. After a few minutes of practice, give them this "new" guideline for asking for numbers: the student asks, "Do you have any multiples of 10 (numbers between eight and 20 work best for younger students)?" If the other player has a multiple (one, two, five or 10), then he must give up his cards. If not, "go fish!"
Mix up a deck of playing cards (numbered cards only) and put them into a hat. In groups of two, ask students to choose one card each. Designate one student as a "numerator" and the other as a "denominator." Whichever student simplifies the fraction first competes against the next student in line. This continues until only one student remains.
Divide students into small groups and give each group a deck of cards. Write a number on the board (any number between 21 and 40 works well). Whichever group adds up the values of its cards using the least number of cards wins.
This game is similar to Creative Blackjack for Addition, but the parameters are slightly different. As with Addition, divide students into small groups and give each group a deck of cards. Write a "starting number" (higher than 40) and an "ending number" (lower than 15) on the board. Instruct students to use their cards to find the greatest number of combined values to get from the "starting number" to the "ending number."