Children are not the only ones who benefit from math games. Math skills are useful for much of everyday life, including balancing checkbooks, working with budgets and looking at loan information. Just because someone is grown doesn't mean that he or she can't have fun learning.
For adults who are into sports, or who follow particular sports, create lessons based around the sports that they enjoy. For basic math skills, adding up scores and looking at stats can work with addition and subtraction skills. As you move up in skills, you can still use sports. Think about algebra with football -- a team needs X number of touchdowns to catch up to the other team, who is ahead by 21 points. You can also use multiplication and division with scores. Baseball stats are good for percentages and averages as well. If you tie problems into sports scores, you'll find games that adult students will enjoy.
For adults who haven't worked with a budget before, you can create fake budgets and play games with a lot of money. Even adults like to pretend that they are millionaires, so give each adult a fake checkbook with a balance of one million dollars. Have them work with investing the pretend money, buying things and saving certain amounts to see who can make their money grow and who will lose it all. These games help adults work with budgeting and also basic math skills like addition and subtraction and multiplication and division.
Stock Market Games
For an adult class in mathematics, playing the stock market is a way to learn about odds and ratios as well as investing money and basic math skills. Information about the stock market is readily available and teachers can act as stock merchants to get the game up and running. Have students purchase fake stocks and then work during the year to see who has invested wisely and who has not.