Yes, WAHOO is a Scrabble word!

Letter values in Scrabble US: W 4, A 1, H 4, O 1, O 1.

Is it a valid word?

WAHOO is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

upright deciduous plant with crimson pods and seeds; the eastern United States from New York to Florida and Texas
deciduous shrub having purple capsules enclosing scarlet seeds
large fast-moving predacious food and game fish; found worldwide

Also: strawberry bush, euonymus americanus, burning bush, euonymus atropurpureus, acanthocybium solandri.