I primarily use olive and canola oil for cooking at home. I'm fairly confident that olive oil is a healthy choice, I'm a little less so for canola oil but it seems like the the best widely available option. I use butter for some recipes and I've been intending to experiment with lard but it's not available where I usually do my grocery shopping.
Most vegetable derived oils are relatively recent additions to the human diet though and one of the principles of paleo type diets is to prefer foods closer to the hunter gatherer staples and to limit intake of foods that require agriculture, and especially of those that require industrial agriculture (a principle that would have led one to avoid trans-fats even before their negative health effects were studied). On that basis I'm inclined to favour animal derived fats until more conclusive evidence of the relative health implications is available.
Plus, I enjoy the flavour of fatty red meats so I will tend to err in that direction given inconclusive evidence on the nutritional science.
I have noticed that among philosophers, vegetarianism of one form or another is quite common. In fact, I became a vegetarian (technically a pescetarian) myself partly out of respect for an undergraduate philosophy professor. I am interested in finding out if there is a similar disproportion in the Less Wrong community.
I didn't request that this go into Yvain's survey because I want more information than just what animal products you do or don't eat; I'd also like to see nuances of the reasons behind your diet. There are a lot more shades than carnivore/vegetarian/vegan - if you want to be a vegetarian but are allergic to soy and gluten, that's a compelling reason to diversify protein sources, for instance. I'd also like to hear about if you avoid any plant foods (if you think they're farmed in a way that's environmentally destructive or that hurts people or if you have warm fuzzy feelings for plants, maybe). Here are some questions that come to mind: