Invincible Lowest Print Run Top 5
While people are trying to find a copy of Invincible #1 (and seeing how Topher already gave us an initial take on what else Invincible to get), here are some other alternatives based on numbers that some people might be missing. I used comichron data for this where available, even though there are a lot of unknown numbers for a few of the editions (Diamond Retailer Summits, for example), but I still think it's interesting data.
EDIT: A few hours after publishing the article Rob Zeida (from the FB Invincible Page) contacted me to let me know that, according to Ryan Ottley, the one with the lowest print run is in fact the 1:100 variant for #100 (number 2 in the top 5). This proves, once again, that the estimations we can get from comichron are just that, estimations, and that it would be much better to get numbers from the publishers, which will never happen. He also gives us some more crazy info: there is a recalled version of 94 that only went to people who worked on the book for comps, so good luck all you Invincible completists and thanks a lot, Rob!
Invincible #75 1:50 Variant
Invincible #100 1:100 Variant
Invincible #100 Comixology Variant
Estimated print run: 10,751
Of course, we had to mention #1. A few more copies out there than Walking Dead #1 (7,266), but still not a lot. Already going for crazy prices and it doesn't seem like it's going to slow down anytime soon. Or at least until people take a look at the Thor: Ragnarok trailer that came out today.
Invincible #1 Skybound 5th Anniversary Editions
Estimated Print Run: ? (anywhere between 50-500)
On one hand these had small print runs, but they are more Nth printings than a good first print #1. In any case, three different editions (color, b&w and blueline) would make for an interesting set for a hardcore collector.