I used snowsuits quite a bit - DS born in December and I can't drive so walked everywhere.
Didn't use the baby bath for more than a few weeks. Never used the top and tail bowl that came with it.
DS loved his moses basket but think next time I'll get a co-sleeper cot instead so transition to cot is a bit easier.
Didn't really use my baby bjorn because my back was fuckered after pregnancy/labour, DS was almost 10lbs at birth, and I hadn't bought the kind which fastens round your waist as well as the ribs. He also hated every single other kind of sling I tried him in (luckily I didn't buy those though).
didn't use the nipple shields I bought. I have tits of titanium clearly.
Barely used muslins - DS just wasn't a sicky baby. Your baby might spew milk like the exorcist, some do, so I'd get some anyway!
The ear thermometer. Waste of money and never worked properly.
The playpen. DS LOATHED it. Keeping it as it might be useful to corral one or other kid if we have a DC2 though.
Mobile. Wasn't in his own cot until he was big enough to stand up and grab the bloody thing and break it.
Breast pump and milk bags. Just could never really get pumping to work, so resigned myself to boobing constantly instead.
Microwaveable steriliser. DS refused to ever take a bottle so only used it a few times for bottles which weren't drunk. Again I'm keeping it because who knows what will happen with DC2!