OY
Worth 5 points before any premium square, and the 12th highest-scoring of 96 — tied with 21 others.
OY extends into 8 three-letter words, which is the 34th least extendable of 96 — tied with 7 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
- B→BOY
- C→COY
- F→FOY
- G→GOY
- H→HOY
- J→JOY
- S→SOY
- T→TOY
No letter after OY makes a word.
Not all of them are equally reachable, which a bare count of 8 hides. OY hooks on 8 distinct letters, and the ones you are likeliest to be holding are T (36% of opening racks), S (26% of opening racks) and G (20% of opening racks). The rarest is J, at 7%.
How often you can actually play it
Out of an opening rack, 5.52% of the time you hold the letters for OY 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
OY backwards is YO, 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.