The one that catches people off guard, but people generally seem to enjoy once they try is dark rum and orange juice (but the OJ has to be good, the kind thats pulpy / thick).
That's my reaction with a jager mule usually. Just a Moscow mule, sub the vodka for jagermeister. It sounds way too much, but the flavors of the ginger and the jager fit so well together, it's really more than the sum of its parts.