4 Letters
100

These letters might help people who are lost while traveling

N, E, W, S

200

Commonly used for movement in PC games

W, A, S, D

300

The orange line of the MTA

B, D, F, M

400

Out of 13, 9 rank with numbers while the last four rank with letters

J, Q, K, A

500

These four letters are the least used in the English language

J, Q, X, Z