The word faultlessness is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 20
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (39 words)
assents, auletes, eluants, eluates, eluents, enseals, falsest, fastens, fatness, fellest, fetuses, flaunts, flenses, fluents, fullest, lateens, leaflet, leanest, lessens, lunates, nestles, netless, salutes, sateens, senates, sensate, sensual, sulfate, sultans, sunless, sunsets, taluses, tassels, tealess, teasels, tussles, unseals, unseats, useless