I voted "wildlife", but really, "nature" would be the best category, as I shoot substantial amounts of "wildlife" (birds, snakes, invertebrates), plant macro, landscape, astro-landscape, all depending on opportunity.
60D: good-light all-around camera, focal-length-limited shooting (birds), good-light macro (love the articulated screen for low angle shots). I have a good normal zoom for this camera, the EF-S15-85, so when I go hiking to a new place and want one camera, one lens, this is the lightweight kit I take.
6D: low-light anything. Astro. Landscape. Handheld macro and close-up, 180mm lens, at ISO 3200 to 25600 (yes, I was shooting hunting spiders and moths displaying eyeshine at night using my headlamp as a light source). I have only FF primes for wide and normal for this camera, so taking a full kit on spec just doesn't happen on a long hike. If I KNOW what shot I want, I will take two or three lenses - my astro-landscape kit for hiking is 6D, 21mm f/2.8, with one or both of Sigma Art 35mm f/1.4 and Samyang 14mm f/2.8.