This newly updated (12-15) resource contains 30 hearts with opposites printed on them. Simply cut each heart in half, mix them up and have students find the matching sides. Can be an individual or group activity, can be used for "I have- Who has"-type of activities, or for "Memory" or "Go-Fish" type card games. Many possibilities for antonym practice.
For year-round opposites practice, try my set of 100 antonyms Opposites for All