What is your favorite esoteric word in your vocabulary?

Naartjie/s

From WIKI - A naartjie (Citrus reticulata, Citrus nobilis), or nartjie, is a soft loose-skinned South African citrus fruit. It is also known as a mandarin, satsuma or tangerine outside of South Africa.

Not that great for day to day vocabulary, but fantastic for scrabble.