Two models for Warhammer 40k are sitting on the "Last Chance to Buy" tab on the GW webstore. The first is the Ork Warboss with Attack Squig, while the second might be surprising to a few, the Broodlord. As it stands right now, the Broodlord is listed on most websites except the US site, where I was not able to find it at all.
I am hoping that these Last Chances to Buy are leading up to something coming..
via Games Workshop
Ork Warboss with Attack Squig
Tyranid Broodlords on 40k Wiki