The word pennyweights 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: 26
Highest Scoring Words With Friends™ Play In The Letters pennyweights
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Seven Letter Word Alert: (28 words)
engines, entwine, ethynes, eyepits, heptyne, hygiene, intense, nephews, nesting, pennies, pentyne, pinenes, seeping, shewing, spewing, spinnet, spinney, stewing, syenite, tenpins, tensing, twinges, weening, weeping, weights, weighty, whinges, whitens