Indium

"So why can’t you buy these nontoxic prank utensils in toy stores, as you could the toxic versions of years past? Price. Indium costs about three times as much as silver. (I get mine from a bulk supplier in China.) Using gallium, you can make alloys that melt in lukewarm water or even in your hand, but it’s more expensive than indium, and it tends to stain the glass and discolor skin. Unfortunately, no alloy replicates the low cost, bright shine and nonstick fun of mercury. Too bad we know now that playing with it for too long can give you brain damage."