I was thinking of attaching a sink spray hose to my faucet's (male) aerator threads, but I am not sure if I need a fitting for it or not. I've tried looking online to see what the standard sizes for faucet aerators are, but I keep getting different answers. Can I have a list of the sizes (In NPT) if I'm using a male-threaded bathroom faucet?
There are many sizes of faucet aerator threads. You can get an idea from the picture of the thread gauge below that you will typically see at a better equipped hardware store where aerator units are sold. (In my experience typical for a USA hardware store. Your situation may vary depending upon your geographical region).
The thread gauge above supports the following thread sizes:
*(F) Denotes stud used to determine female thread size
*(M) Denotes tapped hole used to determine male thread size
Add in metric sizes from other parts of the world and this list is likely to grow considerably.
What are the standard thread sizes used in [tap] aerators?
M20, M22, M24 and M28.
Note that of the 193 nations recognised by the UN, there are still one or two† that still cling to non-standard sizes based on the size of their current or some previous king's thumb or something similar.
You can't mix them. For example don't try to mate a standard sized aerator with your 37/59ths-17¾(T) widdershins faucet. You might get them to connect using your large adjustable nut-rounder and heavy thumb-detector but subsequent removal may require the angle-grinder.
† Myanmar, Liberia and some other such place.