Rhythm Thief said:
Cook and drain your pasta. Put it back in the pan and add two or three beaten eggs, some chunks of cheddar, some cooked chopped bacon, ham or chorizo sausage and some dried chilli flakes. Cook it until the egg is lightly scrambled. Quick, cheap, easy and absolutely delicious.
I'm not sure whether it would work cold though.
<homer> Mmmm, carbonara... <dribble>
I think almost any pasta dish can work cold - sometimes you can just add some more moisture, like a dash of olive oil. I always cook more pasta than I really need, and sometimes I'm good and leave some for lunch the next day, cold. Mostly though, I just pig out and eat it all.
My standby ingredients for pasta would be black olives (get a big jar, keep in the fridge), tinned tomatoes, onions, peppers - red, yellow or orange, and pesto. I nearly always have these in and they make a basic sauce, to which you can add tuna, or minced beef, or diced bacon, or leftover cooked chicken, herbs, chilli, oh, anything you have in really really.
Chicken or Salmon and a creamy sauce is also nice - asparagus and/or broccoli go well with that.
My really lazy dish is cooked pasta with a tin of condensed chicken soup heated up (undiluted) and poured over. My really, really lazy snack is quick noodles, cooked without the sachet of powder, and dumped in a portion of chicken cup-a-soup, made up quick thick. If you liked mushroom, mushroom soup would also do...