Ditto what others have said about a sticky BFP, but if that doesn't happen, DH and I usually agree to buy something together that we see as a 'luxury' rather than a necessity. This year I'm after either a flat screen LCD TV for our bedroom or Sky +, cos I hate setting the video!!
Other than that, I love the usual girly presents - perfume, smellies, pj's and boots vouchers so I can go and treat myself to No 7 products!