Green-crowned Brilliant was one of the less common hummers at Rancho. I only saw it a couple times, but this immature male perched in nice light at one point.
Green-breasted Mangos are another mostly green hummingbird, though shaped very differently: short tailed and long (dark) billed. I didn't see many adult males.
Females and immatures on the other hand were quite common.
I can't think of many birds whose darkest coloring runs down the midline of the underside.