Actually, it's going to be quite a long short-list this year. Over the course of the season, whenever I saw a particularly good play, I made a quick note of the details, and that built up into a solid sampling. However, I certainly didn't watch every inning of every Diamondbacks' game this year, and there's certain to be ones that I've missed, so I'm throwing the list open for other suggestions. If you can't remember the specifics of a particular play, the MLB video page is your friend: you can search for a particular player and/or date [the latter is in the format 11/03/15], and that should then get you down to a range to browse.
You are encouraged to post links to the videos in question in the comments, and also "rec" those suggestions you feel appropriate, as this will be taken into consideration [though be warned - I reserve the right to disregard and/or delete snarky comments like "The trade of Addison Reed"!] Depending on how the nominations fly, and how many we end up with, the format will likely be four preliminary pools of 4-5 plays apiece. These will be posted daily, beginning on Saturday and running through Tuesday. The one in each pool which gets the most votes, along with the best overall second-place play, will make it through to the final vote, which will kick off next week.
These will mostly be defensive plays, due to the nature of the beast, but there are certain to be a couple of offensive ones that make the cut, and I'll even take particularly impressive K's such as Evan Marshall fanning Brandon Crawford with the bases loaded in the bottom of the 10th. Pre-nominations close 1pm on Friday, so I can begin putting the lists together. Remember, this is your chance. I will give short shrift to anyone subsequently complaining "But what about....?" Don't say you were never asked!