The word streakiest 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: 14
Highest Scoring Words With Friends™ Play In The Letters streakiest
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Seven Letter Word Alert: (38 words)
aeriest, artiest, artists, attires, easiest, estates, iratest, iterate, kaisers, karites, reseats, restake, restate, retakes, retasks, retaste, retests, satires, seaters, seriate, setters, sitters, skaters, skitter, staters, straits, streaks, streets, striate, strikes, taskers, tasters, tastier, teasers, tersest, testers, testier, tsarist