Fork

The earliest evidence of forks I've come across is in 12th Century Italy (well OK, Venice, since Italy didn't exist yet). Before this time eating utensils were a spoon and a knife.

However, forks were rather slow to take off. By the 14th Century, France had adopted the fork, but England held off adopting these inventions of the hated foreigners until after the time of Henry VIII.

In period times, people primarily used two pronged forks. However, three, four, and even five-pronged forks are extant.

Since it's rather difficult (and probably non-period) to eat without using your fingers with only a knife and a spoon, a serviette (or at a pinch a tea towel) is an extremely useful item, as it prevents getting nasty hard to remove grease stains on your garb from the roast chicken and making the hospitaller angry (if you borrowed the garb).