An extremely successful Kickstarter project ($41K raised on a $2500 goal, with 36 days left) promises stainless steel chiller pucks to go in your drinks. They're rather nice to look at, and promise not to impart any flavors, nor water down your bevvy. These are rather similar to the (controversial) Coffee Joulies from 2011, and at #8 for 6 "pucs" in a walnut case, it's a somewhat pricey accessory.
Pucs are precision machined from solid 304 stainless steel - the same material used in most medical, dental and kitchen tools. For that reason they are 100% inert, will not add or subtract from the flavor your drink in any way, will not absorb smells or flavors from your freezer, will not rust, oxidize, degrade, discolor, leak, pit, chip, flake, crack or dissolve. They're impervious to every drink imaginable, can also withstand tons of pressure and have a melting point of 1450°F! Pucs are completely dishwasher safe - either clean them with soap and water or give them a quick ride in the dishwasher, then send them to the freezer to re-chill.