Cuba libre? That's just rum and coke with a bit of lime.
Is it really a cocktail?
My favourite is the raspberry beret. Half fill a shot glass with white crème de cacao float tequila on top off the back of a spoon, then place a fresh raspberry in.
If you do it right the raspberry sinks below the spirit but floats on top of the cacao.
You can use other spirits instead of tequila. Pisco or eau de vie are very good.