Students often struggle with synonyms, either they use the same word over and over and over again, or they use the Synonym function on Microsoft Word and end up choosing an inappropriate word.
A great way to fix this is to spend some time teaching them about synonyms (and antonyms if you wish). It's a great way to introduce new vocabulary and is great for discussions about words.
The Synonyms Board Game gives them a chance to thing and practice producing synonyms of various words. All they have to do is roll the dice and produce one, two or three synonyms of the word they land on (each square has a word and a number). So, for example, if they land on a square that says "Love 3" they must think of and produce three synonyms of love.