For solo cooking, I like a Mini-Trangia cookset, with either the supplied alcohol stove or a MSR Pocket Rocket hooked up to an isobutane canister. If confronted with really cold conditions, I would use a liquid gas appliance like my ancient Primus 71L.

For occasional use,I have a sierra cup with a small titanium Esbit cooker and the fixings for a nice cup of tea (/or coffee).