I've tickled several, including my wife, when talking on the phone.
I've tickled my wife's foot under the table in a restaurant when she's trying to order.
In the checkout line, when she is trying to pay, I've stood behind her and tickled her underarm and ribs.
Of course, there is tickling at a movie or concert with my arm around her and tickling her ribs. Or if she makes the mistake (intentional, I think) of slipping off her shoes and curling her feet and legs under her, where I can reach.
When with good friends, I have given her a foot massage while we sit around talking or watching something. I slip in tickles between the regular massaging.
The ultimate for us is when she's inserted a small wireless egg inside her, and we go shopping, and I have the remote control in my pocket and make the egg vibrate. Don't do that anymore, as I brought her to her knees a couple of times in a store. I want to take her to the edge of losing her composure in public, but not over the edge.