Yes, I have had them from tickling alone.
I assume we are speaking of just tickling with no genital contact here. Obviously it is easier to climax if the tickling is combined with genital contact, or even better IMH(orny)O, penetration, as clamping down on something nice and big always enhances sensation during orgasm.
However I have had orgasms, sometimes multiple ones, from prolonged tickling of, to date, my arches, my ankles, my hip/groin area, the small of my back, and my neck and ears- sometimes several spots in combination, sometimes just one spot will do the trick, and all with absolutely no genital contact.
That said, when a big "O" occurs for me during tickling it is always in a situation that has the capacity to become sexual, and it is very much tied into the fact that it is my husband doing the tickling. Therefore if someone with whom I was not involved in this way randomly came up to me and began to tickle me with the expectation that I would soon shudder and moan and collapse, they would be extremely disappointed.