Infamous third lava dolphin
I think my default build, once I have enough notches, is Quick Focus + Longnail + Shaman Stone + Unbreakable Strength. It's just a good all-around build that increases damage across the board and helps you heal without getting hit. For really tough boss fights, where the goal is to avoid taking damage (NKG, Pure Vessel, etc), sometimes I'll go with the "Slash Good" build: Longnail + Mark of Pride + Unbreakable Strength + Quick Slash. Having the extra huge nail lets you keep a good distance away from bosses, which can be very helpful in reducing the number of hits you take. That's especially important against bosses that deal double-damage, since healing becomes a lot more costly and dangerous to do in those fights. As with Dark Souls, the best path to victory is to swing a huge sword and never get hit. Obviously, if you're more motivated by speed, then powering up spells is the fastest way to do heaps of damage. I'm getting better about using my spells in combat, but the real pros find ways to toss in Desolate Dives and Howling Wraiths much more frequently than I ever do.