Most positions can have tickling aspects easily added to them, so this is a pretty wide open field. But some do work better then others.
As Porcelaindoll notes, both the cowgirl positions are excellent, as they have the advantage of making the lee's core ticklish areas available (torso, feet) as a base part of the positioning. They also put the ler in a position where no energy is going into balance or staying in position, so the Ler has much more attention to give to tickling. Also easily modified with simple bondages to make them more effective (arms tied behind lees back at wrists, ankles tied with a short length of rope that goes UNDER the Ler to keep the feet even more immobile.
The Doggie, as she also noted is good, as it provides access to the sides and feet and the weight of the Ler pushing down provides a good deal of physical control. It tends to end in the lee 'crumpling' into an ass up, head on the floor posture, as it is taxing for them to maintain all fours.
The Rocking Horse position is also very good. It's a facing position, usually women superior, that modifies off the facing cowgirl. The difference is that the Ler takes a sitting up position, and the lee matches it, some kneel, others bring their legs around the Ler. This allows (along with solid G-Spot hitting penetrative sex) a pretty free range on the upper torso ticklish areas.
The Right angle position you describe sounds like the T-Square, where the Ler lies on their side perpendicular to the lee, with the Ler partner's hips under the arch formed by lee's legs… wait a picture is worth a thousand words in these cases….
This always access to the feet with a reach around, and torso also.
The Missionary has many variations that awe adaptable to tickling. Most of them involve the lee bringing their legs up against the Ler's chest, or their feet to his shoulders. The Ler, presses in and down with their weight to max penetration, and thus pins the legs tightly. Feet can then be tickled as sex progresses.
But as I said most positions can be modified to the benefit of tickling. Heck even the base '69' allows for both partners to work over each others feet as they proceed with oral attention. It can produce an odd giggley-moaning mess from when I've employed it on couples I've topped.
Myriads