If it has to be Tiffany, then I'd go with the key! It's versatile in that it goes with everything, plus you can wear it either as a pendant or on a bracelet.
As nice as the DBTY is, I second emchhardy's suggestion to look at Brian Gavin - for the same price you can get a bigger, sparklier diamond.
As nice as the DBTY is, I second emchhardy's suggestion to look at Brian Gavin - for the same price you can get a bigger, sparklier diamond.