This drink has to be made and enjoyed a very specific way; if it's not, it'll still be delicious, but it won't work as well.
To be used only in the event that you need to get very drunk, very fast.

Make sure whatever glass you use can hold 6 oz of booze and ice - I usually just use an 8 oz water glass.
Pour 2 oz of coffee liqueur - this must be done before the ice is added. After pouring the Kahlua, add the ice, float 2 shots of vodka, and two oz (or so) of lemon-lime soda.

How to drink properly: With a wide-mouth straw, in one pass.
The reason: Kahlua coats your mouth, so you don't fucking die when you kill the vodka. The carbonation makes your system need oxygen more, which makes the blood pump faster, which translates to alcohol spreading more quickly. Doing it in one go seals the deal.
There you go. Don't move.