Something that is sorely lacking in the "under $5" 3D Low-Poly Assets is UFOs and ships that are alien-looking in design, which could be used as UFOs. I'm making a game that's an homage to X-Com, the UFO series, and Xenonauts, and I think having more spacecraft options would be good; not everything needs to look vaguely like an Earth-based aircraft. As well, some helicopter-style dropships for troop transport would be good, especially with hollow space inside for character models.