I have always loved doing that ... still do, but I've been forbidden to ever do it again.
When I was younger I would tickle my friends who would sleep over. I had one friend who I tickled in her sleep early in the morning. She woke up a few minutes later and told me she had a dream her dad was tickling her feet.
Recently, I tickled my boyfriend under his arms to wake him up from a nap, and he had a dream he was holding a basket of eggs above his head, and I came up and tickled him, and he dropped them all. So he woke up a little miffed at me for making him drop his eggs. xD
A little before that, after having been on here for a couple of hours, I was "in the mood" so I went to our bedroom and tickled the feet of my sleeping boyfriend. He jumped pretty bad and I was concerned that I woke him up, so I left him alone and went to bed. A couple of minutes later I was startled to hear, "Gin ... baby ... I love you, but you just woke me up from a deep fucking sleep because you just had to tickle my feet, and now I can't get back to sleep. I'm going to kill you." So now I'm not allowed to do that anymore. 😀