The most important piece of furniture is a cot / cot bed or Moses basket so that your baby will have somewhere to sleep when he/she comes home.
Cots are usually made of wood. It is preferable if they have the option of 2 or 3 different base heights so the mattress can be lowered as your baby grows to prevent him climbing out. It can also be useful if it has a 'drop side', which means a side of the cot can drop down allowing you to access your baby without having to bend over too much.
Cot beds start off their life as cots, but have the advantage that they can be converted to a junior bed when your little one becomes a toddler. This may save you money in the long run as the bed can probably last until the child is 7 or 8 years old and it can make the transition from cot to bed a lot easier for the child.
Moses baskets are commonly used for babies to sleep in during their first 3 months or so. Many people feel that the baby is more snug and cosy in a Moses basket and they are usually portable so you can put the baby to sleep in different rooms in your house if you so wish.
Other pieces of baby furniture you may want to consider for a nursery include a wardrobe, chest of drawers, bedside cabinet, changing area, shelves, and other storage solutions. Do bear in mind that if you buy furniture from a baby shop it is likely to be more expensive than adult versions in other stores.