Definitely a sling. We had a pouch style and he just loved it. We had a swing, but he could take it or leave it.

A really good swaddling wrap. We used the miracle blanket. When he was tiny the normal wraps were fine but after about a week or two they just stopped being quite big enough, or DS became more squirmy and could get himself out too easily. The miracle blanket solved this for us and lasted us ages.

The other essential we found is a mirror for the car. It means you can see baby in the back seat and they can see you. It stops you worrying so much, and no you won't find yourself looking in it every five seconds, because you can tell when they really need your attention.

And on the opposite end of the scale the things I found were a waste of money for us were:

A cot. We had every intention of him sleeping in the cot in his own room, but when we got him home it just felt wrong somehow and we have co-slept ever since and loved it ever since!! We found out it certainly isn't an essential.

Baby bath - luckily we only borrowed one, but we found it awkward to find a good height for it and so from 2 weeks onwards we took him in the shower with us. And he just loves the shower.