Do her up the wrong'un, doggy-style on her parents' front doorstep.
Also
Take her to an expensive restaurant with one of those remote-control butterfly thingies 'in place', then switch it on high whenever someone comes near
Gag her with own panties whilst fucking her.
Get her to give you a blowjob whilst sitting in traffic on the motorway
Take her to a lapdancing club and get her a naked dance from a girl.
Teach her to give head properly - most girls are terrible to begin with and need lots of guidance and practice. Use a riding crop to tell her when she's getting it wrong.
Come in her hair. All girls hate this, and that's precisely why it's wonderful. You will not be able to stop yourself from laughing afterwards.
Get her to bring herself off with her hand whilst you're doing her up the ass. Both of you will be unable to walk for a good 20 minutes.
Tie her to a tree outside half naked and do her.
If she's really dedicated, get her to take up yoga. The combination of flexibility and core / pelvic floor strength is truely mindblowing.
Screw her whilst she's asleep.
Get a fitball and have sex on it.
Blindfold + Hot wax = fun. But don't use beeswax or colored wax unless she wants 1st degree burns.
Spend all day winding her up and refusing to let her fuck you or come, until she starts to get really frustrated.
Tickle her until she cries, then make her promise to do all sorts of dreadful things before you'll stop.
Make her get a piercing of some sort - tongue or somewhere else, just for your 'entertainment'.
That the sort of suggestions you're after?