An aroma wheel is an amazing invention that helps novice and even expert wine drinkers close in on a specific aroma and inevitably figure out which grape variety you are drinking.
Below is a link to an interactive aroma wheel that will help you pinpoint that pesky scent that you can’t quite put your finger on (opens in a new window):

Popular Red Varietals:
Cabernet Sauvignon
Blackcurrant (Cassis), chocolate, mint, bell pepper, earth; dark colour, heavy tannins and medium to high acidity
Pinot Noir
Raspberry, strawberry, floral, barnyard, truffle (mushroom); light to full bodied, medium high acidity
Syrah
Blackberry, currant, raspberry, violets, hawthorne, spice, meaty, black pepper, eucalyptus; firm tannins, dark colour, jammy fruit in new world wines
Merlot
Cedar, plum, licorice, black cherry, fruit cake; lower acidity and tannin with plump juicy fruit and high alcohol
Cabernet Franc
Lead pencil, cabbage, green tobacco, red berries, capiscum spice; very similar to Cab Sauv with less structure and intensity
Tempranillo
Tobacco, incense-like spice, strawberry, red cherry, and often vanilla and spice; medium to high acidity, medium bodied with elegance and subtlety
Grenache
White pepper, raspberry, spice, high alcohol, juicy and “sweet” fruit with soft tannins and low to med acidity
Sangiovese
Plum, cherry, chocolate, herb, tobacco, gamey and leather notes; medium high acidity, light to full bodied, medium to high tannin
Zinfandel
Aromatic with bramble, spice, sweet ripe raspberry, port-like, berry tea notes; pink off-dry versions and ripe, full bodied, low acidity and high alcohol
Gamay
Red berries, banana & pear candy (from carbonic maceration) green leaf, high acidity, light – medium body, some tannin
Nebbiolo
Tar, roses, truffles, violets, prune and dark chocolate; high tannins, and deep colour in youth – colour fades rather quickly, high acidity
Popular White Varietals:
Sauvignon Blanc
Gooseberry, grass, currant leaf and flint smoke; high acidity, light to medium body – sometimes oaked
Chardonnay
Apple, peach, toast, butter, nut, mineral; medium to full bodied, natural crisp acidity
Riesling
Apple, lime, honey, petrol/rubber with age; high acidity with range of sweetness
Pinot Gris
Nutty, smoky, spicy sometimes honeyed; pale straw through light pink; light to full bodied with range of sweetness, medium to high alcohol
Gewurztraminer
Lychee, talc, rose, perfume and ginger; often a deeper yellow and low acidity and various levels of residual sugar
Chenin Blanc
Wide range of styles from dry sparkling, light dry to sweet and fuller bodied