I have an enormous foot fetish, and am lucky to have a girlfriend with knock-out feet, who takes care of them very well just for me. If she's tied up, I use a variety of tools, the most effective of which is of course the 'leccy toothbrush, particularly if you pull the actual brush off and use the blade underneath, which is particularly effective between the toes. Another torturous device is a small 'bullet' dildo which we bought specifically for tickling, which really drives her mad. It's a bit graphic, (So look away if you have a nervous disposition) but once I'm hard I'll often tickle them with my cock, she says it's unbearable but be warned if you're going to try it - make sure she's restrained COMPLETELY otherwise you could end up with one hell of a kick in the balls!!! If we're just messing around and I've got her face down and I've sat on top of her ankles, I like it old school, raking my fingers up and down her soles at different speeds. Bliss.