Eucalyptus lacrimans (southeast Australia) This rather mysterious snow gum is a close relative of E. pauciflora and its subspecies.  And yet, no one ever hears anything about it.  According to one article*, it may be the same tree that Eucalyptus Nurseries has been selling as E. pauciflora 'pendula'.  If this is so, then we can say that this is a narrow, upright tree with weeping branches and beautiful peeling bark, and that it has been observed in the coldest places in Australia and rivals the other snow gums in hardiness.  -6 to +2°F?
Photos of Eucalyptus lacrimans

Eucalyptus laevopinea - Silvertop Stringybark (southeast Australia) A large tree, esteemed as one of the cold-hardiest stringybarks; though it may be rivaled by the hardiest provenances of E. obliqua and some other rare species.  Has a thin, open crown with a silver cast.  One of the very best eucs for timber, yielding an excellent quality wood.  7 to 12°F.

Eucalytpus leucoxylon Inland Blue Gum, South Australian Blue Gum, Large-fruited Blue Gum, Large-fruited Yellow Gum, Red-flowered Yellow Gum, Water Gum, Yellow Gum (central Australia) One of the hardiest eucs from the deserts of central Australia, where it grows at elevations upwards of 2,000'; and one of the hardiest showy flowered eucs!  It bears clustres of large red flowers at various times of the year depending on climate.  Despite the common names, it is not closely related to either the blue gums or the yellow gums.  A large number of subspecies exist (var. rosea is most common in cultivation), many of which should be tried for cold-hardiness.  Extremely drought tolerant.  Approximately 14 to 19°F.
Photos of Eucalyptus leucoxylon

Eucalyptus ligustrina - Privet-leaved Stringybark (southeast Australia) Useful as a small but fast-growing stringybark; has a relatively thick crown as stringlybarks go.  Probably hardy to around 6 to 12°F.
Photos of Eucalyptus ligustrina

*Irving, Ted. 2000. On Growing Eucalypts in the Pacific Northwest.  Pacific Horticulture, vol. 61, No. 2, p. 42.