Potatoes for versatility.
Aubergines, sliced, marinaded in herby, garlicky olive oil and barbecued and/or made into babaganoush.
Brocolli, I like it as a side veg, I blanche florets and add to salads, and I also use it to make cauliflower and broccoli cheese, to brighten up the otherwise beige-ness.
Sprouts. But only around Christmastime.
Roast parsnips, any time of year.
Sweet potatoes, roast in an old oil drum and bought off the streets in Beijing. Or cubed and dribbled with olive oil and sprinkled with cumin seeds and roasted.