It depends on the mood of the day and on the situation. At work I'll usually have an Apple case (leather most of the time). Right now (summer) it's a raspberry silicon case. I'll occasionally use my Caudabe Lucid Clear as well.
When I'm doing outdoors stuff (weekends, biking, hiking, etc.) I'll use my Spigen Ultra Hybrid.
I have other cases (Peel, etc.) I bought mostly out of curiosity but end up not using them much. I always go back to Apple cases...