Hard drive for the Xbox, it'll last at least a year before the new Xbox makes it useless. The phone you'll just replace in 3 months, and the laptop will have Windows 8 on it and you'll throw it out the window.
I'd say the laptop or the hard drive. The phone you can live without, but I couldn't go without plenty of xbox memory or my computer. You could also save it to get something even better. BTW, happy birthday!