I like to keep an eye out for things when they are on sale, and if I come across something 2nd hand that I can tell is in good condition. I looked at 2nd hand carseats, but they were grubby and I just couldnt trust how old or worn they were - but then saying that, we sold a carseat from our DS that was in excellent condition - but I know alot of people out there dont care if they sell you something shabby or lie about its history ...
Anyway, a cot mattress is important to me to be new and 2nd on the list to be new would probaly be a carseat.

Other things I`ll buy new or get them 2nd hand, depending on what I see and like first.