Vodkatinis
The early decades of the 20th century saw the gradual emergence of vodka in the USA, and as gin is often described as being a flavoured vodka, vodka inevitably found its way into the ever-drier Martini. The result being the Vodka Martini, Vodkatini, or Kangaroo if you'd prefer.
There's more than one story behind the Martini/Vodkatini and the Kangaroo, which, incidentally, was originally called a "Kangaroo Kicker". And, as with most classic cocktails, there are also numerous riffs and variations to explore:
