Merry Christmas. You should download some comic books!
To celebrate, major digital comics apps are selling several hundred comic books for $0.99. Most of them are on sale in ComiXology, the digital storefront that you can access from iPhone, iPad, iPod Touch, Android and any web browser. Dark Horse Comics' app, which you can get for iOS or Android, also has a big sale.
Here's what I recommend you splurge on:
ComiXology There are three big $US0.99 sales running on ComiXology, all through December 30. The most prominently-featured one is called "Marvel Major Players", which includes a long Iron Man run by writer Matt Fraction, a Thor by J. Michael Straczynski, and a ton of Amazing Spider-Man comics. I recommend: 25 issues of Brian Michael Bendis' New Avengers, which are part of a much longer multi-year saga, most of which is available in ComXology (though for the standard back-issue price of $US1.99). Bendis' run is full of all-star Marvel heroes and features a fine mix of sharp dialogue and earth-shaking events.
The Marvel sale also includes a few X-Men-related runs, including 16 issues of writer Jason Aaron's recent Wolverine: Weapon X series. Unfortunately, it's below Aaron's usual excellent standards and only worthwhile for completists who want to read the comics that preceded Aaron's current, stunning run on the more simply-titled Wolverine (which is also in the digital shop, but for $US1.99 an issue.) I recommend: Joss Whedon and John Cassady's Astonishing X-Men run, all 26 issues of which are in this sale. I've read the first dozen, which are well-crafted by the Buffy creator.
ComiXology is running a second sale called "Batman 201", which consists of 201 $US0.99 issues of Batman. There is a ton to go through here, including the very first 1939 and 1940s issues of Detective Comics and Batman that introduced this great character to the world; Batman: A Death in the Family, which featured the death of Robin (the result of a reader call-in vote, mind you!), much of the early-1990s Knightfall crossover which involved the breaking of Batman's back by the villain Bane, who will be featured in next year's Dark Knight Rises movie; early issues of Batman The Legends of the Dark Knight, J.H. Williams-drawn Batwoman issues of Detective Comics and much more.
I recommend: Batman 404-407, better known as Frank Miller's Batman: Year One, indisputably one of the greatest super-hero comics ever made; Batman: The Long Halloween, a 13-issue tour of Batman's villains through major holidays, written and drawn by the wonderful team of Jeph Loeb and Tim Sale (their follow-up, Batman: Dark Victory is also in this sale); the first six issues of current top Batman writer Grant Morrison's recent Batman & Robinrun, featuring former Robin Dick Grayson as Batman and Bruce Wayne's bratty son Damian as Robin; Morrison's stunning, cross-generational, simultaneously pulpy and cosmic Batman: The Return of Bruce Wayne; Scott Snyder's creepy run on Detective Comics, which runs from issue 871-881 and is a precursor to the fine run Snyder's got going now on the New 52-era ongoing Batman comic; the first five issues of Greg Rucka's excellent police procedural Gotham Central (imagine a cop show set in Batman's hometown); Morrison's "Gothic" story from Batman: Legend of the Dark Knight; and, oh yeah, the legendary Batman: The Dark Knight Returns.
And there's one more sale on ComiXoloy. It's labelled the "Holiday Sale" and contains comics from Boom, Dynamite, IDW, Image and Oni, on sale for US$0.99 through December 30. My own tastes usually lead me to reading books from either Marvel and DC or the artsier indies like Picturebox and Drawn & Quarterly. I'll have a tougher time recommending the gems from these mid-tier publishers who are neither as flashy as the big ones nor as unusual and screwy as the art-houses.
From the Boom sale, I recommend you try the first few issues of Mark Waid's Irredeemable, which is about a Superman who becomes the world's most evil man.
I can't vouch for anything from Dynamite, though the highlights appear to be Kevin Smith's Bionic Man and some cheesecake Vamipirella comics.
IDW publishes more G.I. Joe and Transformers comics than I can keep track of (I still don't know if any of them are great), but I recommend the first issue of the anthology Rocketeer Adventures and the first issue of John Byrne's Cold War. (There's also an issue of Locke & Key: Clockworks in here, but having not read any piece of this saga, I can't even tell you where this one fits in, let alone if it merits the acclaim the Locke & Key books have received).
The Image part of the sale has several series I've heard of but never read, so I'm in the same boat as you in trying to deduce whether Who is Jake Ellis?, The Bulletproof Coffin, Robert Kirkman's Super Dinosaur, Elephantmen, and The Blue Estate are worth buying. Image books are wildly unpredictable in quality, so any guidance from readers in the comments below would be helpful!
Oni's standouts appear to be Joe Harris' Spontaneous and Cullen Bunn's The Sixth Gun, neither of which I've read, but both of which I've seen earn praise.
Dark Horse Digital Comics The supposed holiday sale here is 15 issues of Joss Whedon-written (or sometimes simply approved) Buffy: The Vampire Slayer comics, which might be good a) if you're a fan of the series, as these comprise the so-called Season 8 and b) if they actually are selling for $US0.99 cents, which they're advertised to even though the app on my iPad currently shows each issue marked at $US1.99.
I recommend you head to the Dark Horse app's less-prominent "Stocking Stuffer" sale and pick up $US0.99 first issues of Groo: The Hogs of Horder, a few B.P.R.D. mini-series and one of the best Star Wars series ever, the recently-concluded Star Wars Legacy (which centres on a descendant of Luke Skywalker). It's a pity only the first issues are at that price.
Enjoy the cheap comics everyone!