What is the definition of Anniversary Weapon?

An 'anniversary weapon' is like a sentimental sidearm - a weapon that's been with you since the day you were born, and every time you turn 21st, it's your personal reminder of your birthday. Now, here's an edgy example: "I still carry my 1985 Walkman as my anniversary weapon, reminding me that every time I turn 25, I'm still the same kid who once thought my guitar could play 'Smells Like Teen Spirit'."