I remember making up some games using Easter eggs when my teens were younger. So I pulled out the bag of Easter eggs that I re-use every year from our Easter egg hunts and baskets. I took out 15 eggs and wrote a word on each half of the egg, like rich and poor. I used different-colored eggs because antonyms are opposite. I did the same for synonym words like rich and wealthy, but used same-colored eggs because synonyms are words that are similar in meaning. One of her friends came over one day and they had fun playing with these. They entertained themselves for more than an hour. :)
We also used some antonym games and synonym games online. These challenged her a little more. And that's not a bad thing. She actually has been learning new words using these online games. My teenage daughter used this site a lot right before her SATs using the college prep word antonyms. It has words like abrogate and ratify and usurp and dispassionate. I think these games have helped her increase her vocabulary, also, and helped her improve her SAT writing.
I even found some of these games challenging myself. It's one of the things I love about homeschooling. I'm learning right along with my kids in some ways. I've also learned to become a little creative as I try to make up games for them to have fun with as they learn.