This is one of my favorite mechanical pencils that normally lists for $6.99. It has a solid feel in your hand, writes really well, and the lead tip really is difficult to break (but of course it's not "unbreakable" like they advertise). Great pencil at a great deal so I wanted to share.
4.6 stars out of 5 on Amazon (221 reviews). Here's more info from the product page:
0.5mm fine point, standard lead point size, 12 piece tube of unbreakable lead bonus refill for precise and enjoyable writing
Double spring, patent-pending mechanism ensures lead is secure and protected from breakage every time you click to advance your lead
Patented technology eliminates lead breakage regardless of writing styles and angles; Click twice for best results!
Features a lightweight, black barrel with a textured grip for enhanced comfort, and provides a precise and enjoyable writing experience
Recommended refills are Zebra's DelGuard Unbreakable Lead Refill (89881) and Zebra's DelGuard Eraser Refill (83225)