The word mercenaries 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: 18
Highest Scoring Words With Friends™ Play In The Letters mercenaries
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Seven Letter Word Alert: (41 words)
amercer, amerces, amnesic, arcsine, arsenic, careens, careers, carmine, carnies, carries, cinemas, creamer, creaser, earners, enemies, icemans, mariner, marines, marries, meanies, menaces, mercers, mercies, mincers, racemes, reamers, rearise, recanes, remains, remines, renames, rerinse, scarier, seamier, seminar, serener, seriema, sincere, sirname, smearer, sneerer