Recently my step-daughter and her three-month old son (her first child) flew here from Virginia. Fortunately we have a neighbor with a 1 1/2 year old daughter who was willing to lend us the baby "necessities." Wow!! We had an infant seat that vibrated, a swing that operated at different speeds and played music, a special baby bathtub to set in the regular bath tub, a Pack &'n Play portable bed, a little play mat with soft toys attached to "bat" with uncoordinated arm movements, and a "boppy" pillow to use at feeding time. And, all of these were used on a daily basis.
And, of course, he flew here with his required car seat and a sturdy stroller--gate-checked at the airport each time.
But, best of all, the one thing that hasn't changed over time, is the rocking chair. And, this was, of course, the most-used item of all. A good thing we have two of them--one on each level of the house!