I've put my tongue in my girlfriend's arse and given the outside a good lick... unfortunately, she didn't reciprocate... however, she has massage my prostate whilst giving me oral...enjoyed it a lot, but felt uncomfortable about having asked her to do it afterwards.
If she volunteered to fuck me with a strap on I'd be up for it, but would need it to be her idea...
It's also been enjoyable when she's held my hands down whilst riding my cock... dictating the depth and pace, teasing me by holding herself just above the tip, creating real anticipation of when she'd get back on...