Free, open-source, cross-platform, and multi-language analysis tool for Scrabble, Super Scrabble & Literaki. Quickly find top scoring words using given board & tiles. Available in English, French, German, Persian, Polish, Romanian & Spanish.
Gwinch'in also has 3-letter tiles (TTH, DDH, KHW, SHR, ZHR). But ca. 560 native speakers worldwide.
Klingon has 1 (TLH) but approx. 20-30 speakers worldwide.
Catalan has 3-character tiles, see https://github.com/kamilmielnik/scrabble-solver/issues/280