Rinse the raspberries and place them in a glass jar. Pour in enough grain alcohol to cover by a few inches, screw the lid on, and allow to steep 3-4 weeks. Over this time, the flavor and color will leach out of the raspberries, leaving the alcohol a deep ruby color, and the raspberries a weird ghostly pink.
When the raspberries have finished steeping, strain them from the alcohol, discard, and filter the solution through several layers of cheesecloth or, preferably, coffee filters. Measure the final amount of alcohol -- this is your base number. In a saucepan, heat 1.5 times that amount of water, and 1/4-1/2 that amount of sugar, depending on how sweet you like things (note that this is less sugar than required for the puckery rhubarb). To give an example: 4 cups raspberry alcohol would need 6 cups of water and 1-2 cups sugar. Let the sugar syrup cool, then add it to your filtered alcohol. Taste (the flavors will be a bit harsh), and add more sugar if desired. Let age for at least a month before enjoying. Raspberry liqueur keeps at any temperature, but is especially delicious straight from the freezer.