What is your favorite sandwich filling?

I'm not a fan of sandwiches. It's kind of a "necessity" food you pack/ buy on a gas station when you travel or when you're extremely lazy to make real food. Basically something on an instant soup level that doesn't require hot water. 😆 Therefore if I make a sandwich at home, the filling should be something that won't spoil fast on travels and juicy enough to compensate for the dryness of bread. Preferably not too juicy to spill out like a tomato, for example.

Bought sandwiches: soft baguette, some tasty slightly spicy dressing, lettuce, fried chicken strips.