This is gonna sound completely odd, but, it's one of my favourite ultimate concoctions: Macaroni and cheese(preferably Kraft, but, barring that, soya cheese) with rice;sometimes adding vienna sausages or spam if either was on hand, if not, fair enough. I'd make it for myself when I was having an off day when I lived in the States, and it makes me feel gutted when I can't make it for myself now at the drop of a hat.
One of my favourite meals ever has to be the chicken and cilantro rice that my ex's mom used to make.
Ultimate comfort food would be anything that my aunt from Chicago cooked. Total whiz in the kitchen!