My son turned 18 last week.  When I asked him what he wanted on his cake, he said "surprise me."  He is a masonry student at the local vocational/technical school.  He got a chocolate cake with chocolate peanut butter frosting in the middle and fondant "bricks" around the outside.  The fondant was a little too soft.  I think I need to add more powdered sugar and let it dry a little more before I start "construction."