MO
Worth 4 points before any premium square, and the 34th highest-scoring of 96 — tied with 18 others.
MO extends into 14 three-letter words, which is the 19th most extendable of 96 — tied with 10 others. That is the number worth memorising: a two-letter word is a place to put tiles, but a well-hooked one is a place to put them where the board stays open.
Every hook
No letter in front of MO makes a word.
- A→MOA
- B→MOB
- C→MOC
- D→MOD
- G→MOG
- L→MOL
- M→MOM
- N→MON
- O→MOO
- P→MOP
- R→MOR
- S→MOS
- T→MOT
- W→MOW
Not all of them are equally reachable, which a bare count of 14 hides. MO hooks on 14 distinct letters, and the ones you are likeliest to be holding are A (49% of opening racks), O (45% of opening racks) and N (36% of opening racks). The rarest is W, at 14%.
How often you can actually play it
Out of an opening rack, 5.52% of the time you hold the letters for MO outright, the 27th least likely of 96 — tied with 10 others. Counting a blank as whichever letter is missing lifts that to 11.75%, though spending one of the two blanks on a two-letter word is rarely the play. Exact hypergeometrics over the 100-tile bag, not a simulation.
It reverses
MO backwards is OM, which is also good. That is how most of this list is actually learned — 46 of the 96 come in reversible pairs, so knowing one gets you the other free.