The word unrewarding 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 unrewarding
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Seven Letter Word Alert: (40 words)
angrier, darning, dawning, deraign, drainer, drawing, earning, earring, gaudier, gnarred, grained, grainer, grander, grinder, grinned, grinner, guanine, guarder, gurnard, indrawn, nearing, randier, rangier, reading, rearing, redrawn, regrind, rending, runnier, unaired, undrawn, unwaged, unwired, warding, warning, warring, weaning, wearing, wending, wringer