Chocolates, flowers are always good gifts but i have to say i did get a mug from a child i looked after for years with pictures from when they were a baby up until they left the nursery which was very sweet
As a former nursery nurse, if u intend your key worker/favourite teacher to benefit solely, then nothing that u feel u need to split with other members of the team. E.g. Celebrations/chocs end up in the staff room, as does biscuits. A well thought out quirky toiletry or a personalized tea mug are great. Actually something glued and stuck by your child is usually even better received, especially by dedicated staff. Failing that a bottle of smirnoff ice of rose wine are always popular?!!
My colleagues used to like tatty Teddy gifts, make up, primark vouchers, cosyume jewellery (from sainsburys, asda, new look or accessorise) chocolate (in quantity rather than quality) but definitely no ferrero rochet! Hope that helps!
Nice pens are like gold in nurseries. Try to get something to keep, not just something to consume. Mugs are good, also lip balm, or a craft made bracelet. Get your child to help with it or at least sign it if possible, as it makes the gift more personal. I still have gifts from leavers in my last nursery from 5 years ago, and a card made by nursery children when I left work experience there in 1997!