Jumping into places I shouldn't have gotten to and forgetting to save before doing it, trying to take on enemies that could 2hko me, not turning the difficulty down on a scripted dragon fight where as soon as I was in range it would get a kill animation attack on me, pissing off NPCs in that dwemer ruins city (Markarth?) before trying to do some quests there, pissing off the foresworn before completing that little questline, jumping down mountains with horses, playing with autosave off...little things like that.