I've always loved the flavor of well-browned cabbage-like-objects (a.k.a. brassica). Cauliflower and broccoli turn remarkably nutty when grilled or roasted in a hot oven. Brussels sprouts shed their sulfurous reputation and come out sweet and tender when charred in a cast iron skillet or roasted over a hot fire. Stir fried shredded cabbage takes on a smoky sweetness if you let it blacken a bit.
Equally good to grill: bok choy. Working in Chinatown, it's almost my night job to come up with creative ways to use the inexpensive Chinese produce. Bok choy sees a lot of action in my kitchen, and now that the grill is in regular use, it's gonna see a lot of action out there as well.
The key to really great grilled bok choy is to keep it intact so that you can develop some nice charring without totally killing it and reducing it to cinders or mush. I like to split mine lengthwise through the core so that all the leaves stay stuck together. Grill 'em face down, flip 'em, then transfer them to the cooler side of the grill to finish off and you end up with vegetables that have a great contrast between crisp, blackened leave tips, a nicely charred core, and a tender, crunchy center.
A little salt and pepper and a drizzle of good olive oil is really all it needs, but if you want to give it a bit of a Japanese kick, serve it with this sweet glaze made from soy and sake. The sauce, called tare, is standard accompaniment for Japanese grilled chicken or unagi (that is, yakitori or grilled unagi, and it works just as well with grilled vegetables.