Sandwiches are an obvious choice I suppose - egg mayo, tuna mayo, cucumber, ham and cheese, houmous and carrot, coronation chicken, rocket, mozzarella and sunblush tomatoes - with white, brown, seedy bread, wraps or mini rolls for variety.
Cocktail sausages, sausage rolls, olives, tomatoes, skewered chicken, melon wrapped in Palma ham, pinwheels, crudités and dips, samosas / bhajis, bread, cheese / crackers, tortillas.
Quiche, frittata, pork pies, felafel, spinach and ricotta filo pies.
How much cooking do you want to do / buy ready made?
Have a look at waitrose / M&S entertaining platters for inspiration - most of which you could prepare yourself, or just order if it's easier.