The nice thing about Nobel Prizes is that it gets easier to predict them every year, simply because most of the people you nominate don't win and automatically become candidates for the next year (note however that I said "easier to predict", not "easier to correctly predict").
Having said that, there is a Bayesian quality to the predictions since the previous year's prize does compel you to tweak your priors, even if ever so slightly. Last year's award was for a biophysical instrumental technique so that probably rules out similar awards this year.
This year I have decided to separate the prizes into lifetime achievement awards and specific discoveries. There have been fewer of the former in Nobel history and I have only three in mind myself, although the ones that do stand out are no lightweights - for instance R B Woodward, E J Corey, Linus Pauling and Martin Karplus were all lifetime achievement awardees. If you had to place a bet though, then statistically speaking you would bet on specific discoveries since there have been many more of these. So here goes:
Lifetime achievement awards
Harry Gray and Steve Lippard: For their pioneering and foundational work in the field of bioinorganic chemistry; work which has illuminated the workings of untold number of enzymatic and biological processes including electron transfer.
Stuart Schreiber and Peter Schultz: For their founding of the field of modern chemical genetics and their impact on the various ramifications of this field in chemistry, biology and medicine.
Robert Langer for his extensive contributions to drug delivery: Much of what Langer does is actually chemistry, but his practical impact has been on medicine so a prize for him would lie more squarely in medicine. It's clear though that he deserves some kind of lifetime recognition.
John Goodenough and Stanley Whittingham for lithium-ion batteries: This has been on my list for a long time. Very few science-based innovations have revolutionized our basic standard of living the way lithium-ion batteries have. However, prizes for devices have been few, with the charged-coupled device (CCD) and the integrated circuit being exceptions. More importantly, a device prize was given out just last year in physics (for blue light-emitting diodes) so based on that Bayesian argument stated above, it might make it a bit unlikely for another device-based invention to win this year.
Franz-Ulrich Hartl and Arthur Harwich for their discovery of chaperones: This is clearly a discovery which has had a huge impact on our understanding of both basic biological processes as well as their therapeutic relevance. I worked a bit on nuclear receptors myself during a postdoc and appreciate the amazing complexity and importance of their signaling roles. However, as often happens with the chemistry prize, this one could also go to medicine.
Alexander Pines for solid-state NMR: Another technique that has clearly come of age. Using our Bayesian ruler again though, last year's chemistry prize went to an instrumental technique (super-resolution electron microscopy) so it seems implausible to have the same type of prize given out this year.
Krzysztof Matyjaszewski for atom-transfer radical polymerization, Barry Sharpless for click chemistry, Chi-Huey Wong for oligosaccharide synthesis and Marvin Caruthers for DNA synthesis: It's highly unlikely that these three gentlemen will receive any prize together, but I am grouping them under the general title of "organic and polymer synthesis" for convenience.
Matyjaszewski's name has been tossed around for a while, and while I am no expert in the field it seems that his ATRP method has had enough of a practical and commonplace impact to be a serious contender; plus an award for polymer chemistry has been long due. Click chemistry has also been extensively applied, although I am less certain of its industrial use compared to say, the undoubted applications of palladium-catalyzed chemical reactions.
In the world of biopolymers, oligosaccharide synthesis has always been an important field which in my opinion has received the short end of the stick (compared to the glamorous world of proteins and nucleic acids, lipids and carbohydrates have always been the black sheep) so recognizing Wong might be a kind of redemption. On the other hand, recognizing Caruthers for DNA synthesis (perhaps along with Leroy Hood who automated the process) seems to be an obvious honor in the Age of Genomics.
The medicine prize
As is traditionally the case, several of the above discoveries and inventions can be contenders for the medicine prize. However we have left out what is potentially the biggest contender of all until now.
Jennifer Doudna, Emmanuelle Charpentier and Feng Zhang for CRISP-Cas9: I don't think there is a reasonable soul who thinks CRISPR-Cas9 does not deserve a Nobel Prize. In terms of revolutionary impact and ubiquitous use it almost certainly belongs in the same shelf that houses PCR and Sanger sequencing.
There are two sets of questions I have about it though: Firstly, whether an award for it would still be rather premature. While there is no doubt as to the broad applicability of CRISPR, it also seems to me that it's rather hard right now to apply it with complete confidence to a wide variety of systems. I haven't seen numbers describing the percentage of times that CRISPR works reliably, and one would think that kind of statistics would be important for anyone wanting to reach an informed decision on the matter (I would be happy to have someone point me to such numbers). While that infamous Chinese embryo study that made the headlines recently was quite flawed, it also exposed the problems with efficacy and specificity that still bedevil CRISPR (these are problems similar to the two major problems for drugs). My personal take on it is that we might have to wait for just a few more years before the technique becomes robust and reliable enough to thoroughly enter the realm of reality from one of possibility.
The second question I have about it is the whole patent controversy. Generally speaking Nobel Prizes try to stay clear of controversy, and one would think that the Nobel committee would be especially averse to sullying their hands with a commercial one. The lack of clear assignment of priority that is being played out in the courts right now not only tarnishes the intellectual purity of the discovery, but on a more practical level it also makes the decision to award the prize to all three major contenders (Doudna, Charpentier and Zhang) difficult. Hopefully, as would be fitting for a good novel, the allure of a Nobel Prize would make the three protagonists reach an agreement to settle their differences over a few beers. But that could still take some time.
The bottom line in my mind: CRISPR definitely deserves a prize, and its past results and tremendous future potential may very well tip the balance this year, but it could also happen that the lack of robust, public vindication of the method and the patent controversy could make the recognition seem premature and delay the actual award.
Craig Venter, Francis Collins, Eric Lander and others for genomics and sequencing: The split here may be pretty hard here and they might have to rope in a few consortiums, but as incomplete and even misleading as the sequencing of the human genome might have been, there is little doubt that it was a signal scientific achievement deserving of a Nobel Prize.
Alec Jeffreys for DNA fingerprinting and assorted applications: Alec Jeffreys is another perpetual favorite on the list and one whose invention has had a huge societal impact.
Karl Deisseroth, Ed Boyden and others for optogenetics: Optogenetics is another invention that will almost certainly get a prize; its methodology is fascinating and its potential applications for neuroscience are amazing. But its validation seems even more incomplete to me than CRISPR's so it would be rather stunning if they get the prize this year. (On a side note: I am probably among the minority who think that awarding the prize for RNA interference in the 1990s was also too early and quite premature).
Ronald Evans for nuclear receptors: It would be odd if a major class of proteins and therapeutic drug targets went unrecognized.
Bert Vogelstein, Robert Weinberg and others for cancer genes: This again seems like a no-brainer to me. Several medicine prizes have been awarded to cancer genetics so this certainly wouldn't be a novel idea, and it's also clear that Vogelstein and Weinberg have done more than almost anyone else in identifying rogue cancer genes and their key roles in health and disease.
A brief note on the physics prize: There is no doubt in my mind that the Nobel committee needs to give the prize this year to the ATLAS-CMS collaboration at the LHC which discovered the Higgs boson. A prize for them would emphasize several things: it would put experiment at the center of this important scientific discovery (there would have been no 2013 Nobel Prize without the LHC) and it would herald a new and necessary tradition of awarding the prize to teams rather than individuals, reflecting the reality of contemporary science.
So that's it from my side. Let the games commence!
Note: Reader artqtarks has a list, with a thoughtful analysis of potential prizes for CRISPR and tumorigenic genes.