Okay...
"You have really hot feet."
This is a compliment. However, there are two problems.
It's not like saying "You have beautiful eyes." Eyes are a common thing to receive compliments about and therefore it is more acceptable. feet, on the other hand, are very rarely commented. Therefore, a woman is much less likely to be receptive to such a statement.
Secondly, using the word "hot" will get you NOWHERE. "Attractive" would be a better choice, but "sexy" would be best. Even then, you can't just randomly say shit like that! It has to be in context, like at a bar, with someone you're talking to for a while, or someone you've struck up conversation with at least.
In today's society, random, un-fished for compliments are generally frowned upon, thanks to most complimenting men being creeps. So, as in many cases, the creepo many have ruined it for the chivalrous, kind-hearted few.
Furthermore...
"Are they ticklish?"
Okay...I'll reserve my wise ass crack about this one.
However, asking this of a random woman is ten times are strange as an unsolicited compliment, no matter what the context. The chances of it succeeding are ridiculously slim. It's worked for me everytime but only because I have tried it twice and with EXTREME discression. Only someone who honestly knows what they are doing with a woman in conversation can use this and if you need to ask if it works, you are not one of those people.