Just saw this on the BB Ad for this week. Get a $5 Best Buy GC when you buy a $25 iTunes GC. I don't see this online so it must be in stores only.
Here is the online: http://www.bestbuy.com/site/olspage.jsp?id=pcmcat201200050005&type=category&AID=10744579&PID=3080846&SID=4003868278&ref=39&loc=01&URL=http%3A%2F%2Fwww.bestbuy.com%2Fsite%2Folspage.jsp%3Fid%3Dpcmcat201200050005%26type%3Dcategory%26AID%3D10744579%26PID%3D3080846%26SID%3D4003868278%26ref%3D39%26loc%3D01