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Unless you plan on co-sleeping or already own a crib and plan to use it from the start, a bassinet is a must have for those first couple of months.
Of course a car seat - and don't worry, there are some really attractive gender neutral ones out there. You can even buy covers for your car seat after the baby is born to boy or girl it up.
Bottles, even if you plan on breastfeeding you should have a couple around just in case to use for pumped milk or formula if something isn't working out.
Diapers, cloth or disposable. If you're using cloth, you can buy all your infant diapers in gender neutral colors, and then register for or buy boyish or girly one-size or larger sized diapers. One-size often don't fit real well on newborns anyway,

You need very little to get started, I found it most useful to keep my son dressed in sleep and play type outfits with zippers, those with snaps can drive you crazy, especially in the middle of the night!
Bath towels and burp cloths are always good, as are teethers and baby bath products. Those don't have to be gender specific and you can always use those.
Regarding the car seat covers, it isn't recommended to add anything aftermarket to a car seat, it can impact the effectiveness if you are in a crash. If you need a cover, you can get the "shower cap" type ones to shield from the elements.
Regarding the pump, this is something that you have to see if you even need...you can always rent one from the hospital and in some cases, it is covered by insurance.
FWIW I didn't have a formal registry or shower and we didn't find out the gender either. It does save you from overbuying just because the dress is cute and pink!

eta: a swaddle blanket is also a good item to have. your kid may hate it, but you might need to try something in the middle of the night.

You need very little as far as clothing, and I'm sure most of the newborn layette type stuff is already gender neutral. For your bigger items, it's a good idea to get gender neutral anyways, since then you'll be able to use it for future children (or sell/gift to others if there are no other babies in your future).