Windows Explorer (the one in Win8.1, at least) won't allow creation of files with a space at the beginning or end of a name, but it's definitely allowed in the filesystem. For example, from a command prompt, this works:
echo hi > " hello.txt"
Explorer can see this file and perform operations on it, but if you try to rename it to a name with leading or trailing spaces, they get trimmed.
I have used '~' to cause files to sort at the top - this seems to be some oddity of the sorting order that Explorer uses, since ~ would sort at the end in ASCIIbetical order - but at least it's an allowed character at the beginning of a name in Explorer, unlike space.
I have used '~' to cause files to sort at the top - this seems to be some oddity of the sorting order that Explorer uses, since ~ would sort at the end in ASCIIbetical order - but at least it's an allowed character at the beginning of a name in Explorer, unlike space.