Depends who it is for.
If it's for a kids party, I tend to do :
fairy cakes/buns
cocktail sausages and cheese on sticks
sausage rolls
cherry tomatoes
crisps (various types)
sandwiches (various types) cut into triangles
jelly
mini scotch eggs
chocolate fingers
If it's an adult party I do :
a large tureen of bolognese, with nachos, so people can get a bowl of bolognese for themselves and dip nachos in
nibbly crackery things like prezels, ritz biscuits, stuff like that
sausage rolls
quiche
houmous (various types) and carrot sticks
mini pizzas
crisps
buns
chicken drumsticks / bbq chicken drumsticks