Just a little question.

When ive a fat man and a mirelurk attack me. i go to my pipboy i stock my fatman and i fight the mirelurk with my hand. But exist it a keyboard shortcut for doing this action?

I'm a console player and we have a hotkey for switching between 12 different items. I'm positive PC players( are you on PC? ) have the option of setting up hotkeys for weapons, items, grenades etc.

No hotkey for bare hands. On PC there's a mod that lets you equip and hotkey the "bare hands" weapon.