I'm interested in what kinds of Russian words you know that are particularly unusual compared to other words in the language. Here are a few that many Russians know about, but not all that many students know.

There are several words in Russian that have three e in a row:
змееед - snake-eater
длинношеее - long-necked (neuter)
короткошеее - short-necked (neuter)

There is only one word that has the -ко- infix:
закоулок - alleyway

A verb without a root:
вынуть - to get out, take out

Anyone have any other interesting words to share?