The Magic Merlin Sleep Suit. If you haven't heard of it, it truly is magic. Recommended for that stage when your baby grows out of a swaddle but is still flailing their arms around and waking themselves up, this is the answer. They can only wear it until they can roll over in it, but we hit that point with my first and I was considering cutting the arms off of it so he could keep wearing it. That's how much I loved this thing. $40 (and they have next day shipping)
Okay to Wake Alarm Clock
didn't believe that my toddler could have access to getting in and out of his bed and somehow would wait until a certain time to come out. Turns out, with this alarm clock, he waits "until my light is green" nearly every day. It's magic. Trust me on this and get this version and NOT the one that looks like a car with a traffic light. That one is impossible to use and set. Plus, this one has a nap timer option too, which is invaluable. Very easy to use, and around $25.
Merino Sleep Sack
I'm conflicted about this one. On the one hand, I Flove our merino sleep sack. It's the EXACT right weight of thickness, winter or summer. The zipper placement on the side is so easy to deal with (way better than halo) when putting them to sleep or in the middle of the night for a changing. My caveat is that we bought ours used. I went to look at the price and it's $90. Ouch. I'm basically endorsing this as a "baby registry" item only.
Rock and Play
My favorite and most indispensable baby item, the rock n play. It's a glorified baby hammock, but both my kids slept so soundly in this until they were about 3 months old and outgrew it. But they slept great cocooned in it. I asked my pediatrician if I should worry about the "not a flat surface thing" and she looked right in my eyes and said "whatever gets you sleep". So, that's my non-AMA endorsement. But seriously, for $50, this is the best.
Black Out Curtains
Black out cutains are Crucial. These are the ones we use, with painters tape on the edges. Not fancy but effective.
Travel Black Out Curtains
For traveling, we bought a set of these (it's a 6 pack) which are black out curtains you can cut to fit pretty much any window space. They stay up WAY better than the travel suction cup options, and you can just throw them away when you leave because they're paper. You can also use plastic trash bags, but they don't always fit perfectly, and they also create a "meth house" vibe that's a little creepy. $30 for a six pack.