A skin-marking device is disclosed that has a holder body and cap having a shape other than round, preferably triangular, to prevent the device from accidentally rolling off a flat surface. Measuring indicia is disposed on the device for accurately measuring distances. The device contains a dermatologically acceptable coloring agent for marking a patient's skin and one that may be selected from the group consisting of a radioopaque substance for x-ray diagnostic purposes, a fluorescent composition, a non-magnetic hydrogel for nuclear magnetic resonance imaging diagnostic purposes, a sterilizable gel ink, a combination of any of these, and a mixture of any of these. The holder body or cap may include a pocket clip or magnet attached thereto to permit the skin marker to be clipped inside a person's pocket or prevented from sliding off a magnetic drape or other magnetic surface, respectively. The skin marker may also come in a number of different sizes, one of which is optionally short enough to allow it to fit into a needle counter box to be packaged as part of a mini kit.