I was a Girl Scout Troop Leader for a number of years, and each year when we went on an overnight we needed to have something to identify our troop, especially when we went to large events where there were lots of other troops. You can only do so many tie-dye t-shirts before it get's a little much. One of my secret weapons to making things more fun and different was to always have these Marvy Fabric Markers!!
One year Old Navy was selling these vintage t-shirts that had the Girl Scout cookies on them, well, I bought a ton of them in one color for our troop. Then at a meeting each girl got one, and we took the Fabric Markers and wrote our Troop number and area on the front and a nickname for each girl on the back. Even though that was many years ago, and those girls are no longer scouts, and I am no longer a leader, they tell me those were their favorite shirts!
I have also used these markers at birthdays parties. Have a plain t-shirt, and when the kids arrive, have them "sign-in" on the t-shirt to the guest of honor. This way the birthday child has a special shirt to always remember this birthday party and the friends that were there. An updated take for older parties is to use a pillow for teen sleep-overs.Be creative, these markers will write on just about any material, cotton and cotton blends.
These markers are wonderful to work with, it's just like writing with a regular marker and they dry and set to permanent. The item can be washed over and over again later.