I've given away FastPasses and Ponchos, offer to take family photos and occasionally paid for the meal or snack behind me but my favorite way to give magic is to simply engage people.
On one trip I noticed an older woman with her grown daughter and her daughter's family. This woman looked so pretty: well groomed with a matching necklace and earrings...so I tapped her shoulder and said I just had to comment on how nice she looked. Well.....her eyes got a little teary and she proceeded to tell me that her husband recently passed away and since he usually accompanied the family on their Disney trips she was hesitant about going alone...she gave me a big hug and said that every morning her husband would tell her just how nice she looked and that she "knew" my remark was his way of telling her that he was still with her.
I felt like a million bucks...so simple...just to reach out.
Thanks OP, for starting this thread!