1. Sports man!
2. Comical exaggeration of political figure!
3. Super heroic imaginary adventurer!
4. Ethnic/racial stereotype!
5. Shabbily assembled version of briefly popular film character!
6. Ditto ditto ditto ditto ditto ditto ditto television ditto!
7. Female archetype, only SEXY!
8. Conceptual joke that is actually not a costume at all!
9. Giant pretzel! (Bavaria only.)
10. Fat loser who lives with his family!
Also, I tell you what: there is nothing. NOTHING. More sadly amusing than looking through on-line archives of scifi/comic convention costumes. Thank goodness I live in America during the internet age, where someone even lamer than me is only a Google search away.