It's an old one, a true classic cocktail, called "The Last Word"
Equal parts:
Gin
Chartreuse (green)
Lime Juice
Maraschino Liqueur
Shake with ice, serve straight up.
Abso-fucking-lutely perfect!
And, of course, because of the Chartreuse, there's no sense using the high end gins like Sapphire, Plymouth, Hendricks, Magellan, Zuidam, Genever, Tanqueray, and so forth - the subtleties will be lost. Those really are gins best used in Gin and Tonics, Martinis, and Aviations.
Use a cheaper gin for this one.
You could probably do okay with Vodka, though I wouldn't suggest Stolichnaya or Svedka, or any of the really cheap vodkas (but that goes without saying - one should not use the "really cheap" versions of anything in anything). I should think that 45th Parallel Vodka (
http://45thparallelvodka.com/) would be a perfect vodka for this drink.
Seriously, people - it's just as easy to drink and eat GOOD stuff as it is to eat and drink the shit.
Why not opt for what is good?
Seems a simple decision to me.