I use a flogger, even just to run over their body. Blindfolds, pinwheel, nipple clamps/clothes pegs, vibrators, I've got a couple of little things from Ann summers one is like a little Pom Pom and the other is thing strands of metal beads/chain which feels nice. If I want to mix it up I'll add a little bit of chocolate (check for allergies/dislikes first) for smell and taste and if they're comfortable, add earphones with some music to mix up their senses. I've used one of those head massagers in the past too, you can pick them up pretty cheap.