What It Scores
ZZZ is a valid word in the tournament list this site uses. Tile values only, before any premium square: 30 in Scrabble and 30 in Words With Friends. The letters break down as Z10 Z10 Z10.
Longer Words Containing ZZZ
ZZZ appears inside each of these, which is what makes it worth knowing as a hook.
Next: the Word Unscrambler for any letters at all, and the two and three letter lists. Full entry and definition at Merriam-Webster.