Yogurt! Not only doesn't need cooking, but doesn't take any effort to eat. Soya version if you don't do dairy (I say confidently, having never knowingly had anything labelled Provamel pass my lips). That tends to be my choice on weekdays unless I have some good leftovers that I can take to work and microwave.
Yesterday's leftover veggie spag bol/bean risotto/kedgeree.
Tuna sandwiches.
Whisk up a milkshake or a smoothie. Easy to throw down 500 protein-rich calories that way. The Liz Applegates of this world would probably advocate throwing in a few spoonfuls of powdered egg white. I think that's gross, personally, although...
Eggs, eggs, eggs! Less than a minute to poach in the microwave, or fry in just a spot of oil.
Stick a tuna and haricot bean pizza in the oven while you have your shower. Sorry, Michelle, if you're reading this, I know your feelings on my tuna pizza fixation.
Beans on toast. Food combining at its most accessible.
A bread roll filled with cottage cheese (no spread needed) and something to give it a bit of flavour.
Any more ideas, anyone?