What type of gift can I give my aunt and uncle who have been my guardians for 7 years.?

I will graduate from high school next year. I want to find a special gift for my aunt and uncle who have been my guardians for the last 7 years, since I lost my parents. The transition from being an only child living on the east coast to becoming the oldest child of 5 living in the midwest was difficult and I wasn't exactly real open to my new situation. Through it all, especially the first 15 months my aunt and uncle were there no matter what. Even when I ran away after 4 months, when my uncle caught up with me and I was sure I was headed for the proverbial woodshed, they just sat me down and helped me work through the problems I was having. They have been more than my guardians, aunt and uncle. They have been parents to me just like they are to their 4 sons. I have told them many times how much I appreciate everything and how much I love them, but when I graduate from high school I want to do something special for them. Money will not be a problem because my parents left me with a substantial trust fund plus I have plenty of my own money that I have earned over the years. I want to give them a gift that will tell them how much they mean to me and how much I appreciate everything they have done for me. Please let me know your ideas.