Oil. In Greece it's always olive oil, elaiólado (ελαιόλαδο) unless otherwise stated; παρθένο ελαιόλαδο (parthéno elaiólado) is virgin olive oil.
There are never-ending arguements as to who produces the best. Nineteen olive oils from around Greece are designated PDO: Crete, Halkidikí, Kalamáta, Lygourió, Laconía, Kefaloniá, Olympía, Lésvos, Préveza, Rhodes, Thásos, Sámos, and Zákynthos
Some other kinds of oil:
αραχιδέλαιο (arachidélaio): peanut oil
έλαιο καρυδιάς (élaio karydías): walnut oil
φυστικέλαιο (fystikélaio): vegetable oil
ηλιέλαιο (iliélaio): sunflower oil
λάδι κανόλα (ládi kanóla): canola (rape seed) oil
λάδι καρύδας (ládi karydas): coconut oil
μαγειρικό λάδι (mageirikó ládi): cooking oil
καλαμποκέλαιο (kalmbokélaio): corn oil
σησαμέλαιο (sisamélaio): sesame oil
σογιέλαιο (sogiélaio): soy bean oil
Image by stevepb