I’ve recently acquired some nipple stimulators which are basically suction cups with rotating brushes in the top.
I set the brushes going on an alternating patter (my favourite) then gradually pump the air out so that my nipples are sucked up into the brushes.
I start with them barely touching but as I get more excited I suck them up to get a harder more painful contact.
Once or twice I’ve ended up with sore or bleeding nipples but the sensation is amazing and totally worth it. I can come easily using this toy.