Underwear definitely!
i try to encourage my mrs wearing nice underwear as often as I can, buying her nice things and often leaving them out when I go to work so she knows I want them on her when I get back.
My GF used to wear sexy lingerie and maids outfit for me but then she fell pregnant and she hasn't done since. Until recently that is.
She now wears sexy lacy panties for me and likes me to masturbate onto them for her whilst she wears them.
I'm trying to introduce more lingerie into our love life as I absolutely adore to see a woman wearing it. She flatly refuses to get a corset though as she says they look like they would be too uncomfortable. Corsets are (and always have been) my favourite lingerie item. 
In bed I'm usually naked but she likes to wear a onesie when it's the colder months and in the warmer months wears shorts and t-shirt type pjs. This has only happened since last summer as she used to wear full pjs in the warmer months.