intact whole grains:

soft: buckwheat, farro, grano, Kamut, millet, oats, rice, soft wheat, spelt, wild rice

hard: barley, corn, durham wheat, rye, triticale, wheat

tiny: amaranth, quinoa, sorghum, tef

abundant water: oven?,saucepan, steamer

just enough water: microwave, oven, rice cooker, saucepan (e.g. chelu rice)

brown plus just enough water: microwave, oven, rice cooker, saucepan

no water at all: popping

I'm a cook, not a food scientist, so I tend to find one way or two ways of cooking and then stop experimenting. A determined researcher could cook a different grain a different way for more than a year – and that's not counting different kinds of liquid, different ways of browning, different ratios of grains to liquid, different cooking times, and different resting times.