If only their parents had waited until summer to conceive! Still, they can't change their birth date, but you can most definitely ensure they get the best two presents for their bi-celebration this December.
BTW, if you hate the gallery format as much as they hate being Sagittarians, click here.
ION USB portable turntable and Zumreed headphones If your pal has lots of records, the USB turntable will help with backing them up and making digital copies, which can be transferred easily to a Mac or PC. And of course, they'll be needing stylish 'phones, too. [ION $140 and Zumreed $60, both at Urban Outfitters]
Griffin AirCurve and iTrip Autopilot Any iPhone or iPod owner is bound to be happy with a couple of accessories from Griffin. Take the AirCurve clear acoustic amplifier, which acts as a speaker with no batteries required. Combine it with a car accessory for Christmas, such as the iTrip Autopilot, and you're onto a winning match. [AirCurve $19.95 and iTrip Autopilot $99.95, both at Apple]
Optoma PK-101 and Samsung N310 Give the gift of film this birthday/Christmas, with the Optoma pico projector connecting to the Samsung netbook with ease. The netbook may not have an optical drive so DVDs aren't playable, but there's no stopping your recipient from downloading or live-streaming some films, to beam onto a wall in 480 x 320 resolution. [Optoma $229.99 and Samsung N310 $349.99]
Diana F+, 38mm super wide lens, and instant back+ Lomography is the recent revival of a '60s photography craze that results in the most brilliant photos. The Diana F+ is the most classic model, and pick up a few accessories while you're at Lomo's online store, including a super wide lens and instant back+, which produces instant photos a la Polaroid. [Diana F+ $95, super wide lens $40 and instant back+ $95]
Red Square superyacht and Bell-Boeing 430 helicopter What, your friend doesn't mean enough to you that you'd splurge $930m on their birthday present? And then another $2m on their Christmas present? Shame on you. [Red Square €630m, Bell-Boeing 430, around $2m]
Star Wars DVD boxset and Tauntaun sleeping bag Yes, we love Star Wars as much as the next person, but with the trilogy expected on Blu-ray anytime soon, we wouldn't go suggesting you buy a DVD boxset that's been around for years, would we? Nor would we recommend a Tauntaun sleeping bag as being conducive to a love life. [Star Wars DVDs $25.99 and Tauntaun bag $99.99]
PSPgo and $50 PlayStation Network gift card Giving a gift card isn't the most thoughtful present, true—but how else would you give digital downloads to someone, hmm? They should be so happy with the latest generation of PSP, they won't even notice that $50 only gets them a couple of games. [PSPgo $249.99 and PlayStation Network card $50]
Sony BDP-BX2 Blu-ray player and Battlestar Galactica Blu-ray boxset I've just finished watching BSG on Blu-ray, so can vouch for how incredible it looks in HD. Coupled with a Sony Blu-ray player, you're giving any sci-fi nut the perfect viewing experience—provided they have an HDTV, of course.
Don't forget to recommend your own favorite gift ideas for people with birthdays in December in the comments—include pic and pricing if possible.
All Giz Wants is our annual round-up of favorite gift ideas, including amazing attainable objects and a few far-out fantasies. We'll be popping guides catered to different interests several times per day for the next week, so keep checking back.

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