A long time ago a dermatologist used liquid nitrogen to remove a plantar wart from my foot. Another one I saw later used to carry a spray bottle of liquid nitrogen around with him in his lab coat. There must be quite a number of things LN can be used for if he carried a bottle with him to be right at hand.
What are the conditions for which LN is a common treatment in standard dermatology practice today?
[Seborrheic keratosis](Seborrheic keratosis) is one.
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Maybe because duct tape, although more effective, seems a bit too ghetto 
My doctor used it to remove skin tags from my neck and other places.
Here’s what I have used in the past for poor man’s cryotherapy. I don’t know about warts, but for cysts I have used a large Ronson butane canister (for refilling lighters). It is a bit difficult to get purchase on the little plastic tip, but if you can spray the butane on the cyst it should clear up after a couple of days. Don’t let your fingers get frost bitten manipulating the tip.