I've selected "whisper" as a medium difficulty word for Hangman. It's 7 letters long and contains a mix of common letters (i, e, r) and less common ones (w, h, p). The "wh" beginning might not be immediately guessed. While it's a familiar English word that everyone knows, it's not among the most frequently used words in everyday conversation, making it challenging but fair for a Hangman game. It meets all the criteria: it's between 4-10 letters, contains only standard English letters, is a real word (not a proper noun or acronym), and has no special characters.