Ever bent down to pick up a fallen ice cube, only to stand back up with it stuck to your hand? It's a phenomenon that doesn't make a lot of sense at first thought, since our body temperatures run a lot warmer than ice cubes. However, there's some serious science behind why this happens with some cubes, but not others.
There are a couple of factors that determine whether a run-in with ice will leave a person totally unscathed versus looking like the second coming of the "Frozen" character, Elsa. First being, the temperature of the ice cube. That's right, although water freezes at 32 degrees Fahrenheit (0 degrees Celsius), ice can actually achieve temperatures much chillier than that. So, the colder it is, the more likely it is to stick to skin upon contact. The "warmer" it is (or warm for ice, anyway), the lower the chance that it'll stick.
The other variable at play is the moisture level of the skin. Even if you haven't just washed your hands, your skin likely features a tiny bit of natural moisture, in the form of sweat. So, when the cold ice comes into contact, it causes said moisture to freeze and thus stick to the skin. Basically the oxygen and hydrogen atoms in the water molecules in the ice want bind to hydrogen and oxygen atoms in the sweat on your hand. And hydrogen atoms form strong bonds!
Don't panic, however, as this is not nearly as unfortunate a situation as the old tongue-stuck-to-the-telephone-pole conundrum. Most of the time, the ice will just fall right off after a second or two because the natural body temperature will cause it to melt. If the cube is being extra sticky and stubborn, however, simply run some warm water over it and you'll quickly enjoy sweet, sweet freedom.