Interesting ceramics are for sale at Hephaestus, on the waterfront, at 21 May; Alexander's, on the corner of Plateia Museio (the square 1 block back from the waterfront); and the Mistral, 6 Vironis, up the hill opposite the post office, offering the work of the potter/owner.
For a taste of the local cuisine, consider Kefalonia's prized Golden Honey, tart quince preserve, or almond pralines. Another possibility is a bottle of one of Kefalonia's highly praised wines. You can visit Calliga Vineyard (selling white Robola and red Calliga Cava) or Gentilini Vineyard (with more expensive wines), both near Argostoli; or Metaxas Wine Estate, south of Argostoli. The tourist office on the waterfront will tell you how to arrange a tour.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.