I've just finished an experiment with Sloe Vodka, which has so far been a hit with everybody who has tried it (about 2 dozen people so far).
Its quite easy to make as follows.
Make Sloe Gin as per normal to your favoured recipe
(Mine is 2 lbs of Sloes, 8 oz sugar 1 Litre gin)
When you decant the sloe gin, keep the sloes in the container, add a second helping of sugar and a bottle of cheap vodka.
Leave for 6-12 months, remove the liquor and drink.
Mine has quite a smooth flavur, followed by a swift kick of and after taste!
Enjoy!
Dave