• I look like a weapon if you know how to handle me (Edit)
• I am most popular than any other
• People use me often when they want to be informal
• Dirty minds see something lascivious in me
• I am loved by road trippers
• Some isolated people in the world have never seen me
• I am man-made and when I am with my friends I can enlighten you
• I have trillions of twins, but they are mostly fraternal twins
• I am indivisible but I can become something else if you mutilate me (edit)
• I am often the beginning of some ends, but I am not the apocalypse (edited)
• My grandgrandfather spirit is hidden in multiple things, like trees
• I've been 16 for long time now, but that depends on the mood, on self-confident days I pretend I am 80, on miserable ones 112, etc...

What am I?