I make a whiskey that has a 2" stick of vanilla bean, a teaspoon of pure maple syrup and a handfull of raisins per 4 litres of 65%.
Must admit, it's expensive but sooooo much better than vanilla essence.
It is nice to drink straight and the vanilla really comes out when mixed with coke.
It was an attempt to get a JD type sweet whiskey. It's now my "special occasion" sippin whiskey.
As for Bourbon - I don't flavour that with anything except charred oak.