In prehistoric times, early humans would indicate ownership by drawing a human head on an object with charcoal, whacking the head with a club, and dragging it back to his or her cave. Today's Groupon lets you leave your mark in a more dignified manner: for $15, you get $30 worth of customizable, laser-engraved keepsakes from addaLine. Purchases require a PayPal account, and part of this Groupon's value may be applied toward shipping.

The addaLine staff uses a CO2 laser machine to create custom engravings on many different mediums, including wood, marble, leather, granite, glass, tile, metal, plastic, and passed-out friends' faces. Gift-seekers can browse the online shop for creativity-kickstarting suggestions such as stylishly embellished aluminum sports bottles ($15), personalized pendant necklaces ($15), and coffee mugs ($9.95) customized to say anything from "I Heart Mondays" to "World's Greatest Dictator." You can also create one-of-a-kind tokens that are as stylish as they are functional, such as an engraved pocket knife ($22.95) or an elegant brass door knocker ($29.95).

Every addaLine creation is individually tailored to match the customer's specifications, with 21 font choices and multiple graphic possibilities. Several gifts can even include beloved photos to create lasting memories of family reunions or the time your boss got his hand stuck in a stapler. The addaLine engravers are always up for a challenge, so hotdog-eating dares and new gift ideas are always welcome.

This Groupon is redeemable starting 24 hours after this deal closes.