Here's a funny but practical glitch that I've found. While you're sprinting with your handgun, go prone so you fall on your knees and then you quickly press Ctrl + W key. You're going to do a front flip into the ground and you'll finish on your back ready to fire. I found this issue while I was searching for the quickest way to go on supine position, maybe a specific key and a animation like falling on your ass would be really nice to use.