How do you define need? If you mean "need" as in for emergency preparedness or utility, then one from every major category would indeed be enough. Right now I am just working on getting a good light for each category, then I'll probably have enough lights. Of course, there are subcategories, and there is always a better light in each category: one that is smaller, one that is brighter, one that runs a few hours longer, one that has more throw, one that has more flood, one that is lighter, one that won't break very easily, one that is cheaper (so you don't have to be as afraid of losing or breaking it), one that has a pocket clip to keep you from losing it, one that emits colored light for specialized uses (i.e. red for stealth and improved night vision), one that glows in the dark, one that is rechargeable, one that goes on your head, one that mounts on a bike or gun, one that improves color rendition, one that's regulated, one with a smoother beam, and so on and so forth. Then, of course, you get into the realm of the hybrids, where a light combines several categories into one, such as the A2's bright incandescent and long-running LED's. Of course, every one of these lights is an improvement, just a little better for a particular situation than anything else you have. You "need" every one in some way or other. Of course, I haven't even touched on the category of lights that are purchased solely because they are a novelty, look really good, or are just plain awesome and fun to play with. So, "need" is something that could be taken to mean the bare minimum that you can get by with (and even that is subjective), or it could mean everything you have a genuine use for. Really, the deciding factor is how much money you have and how much you're willing to spend. Hold on to your wallet, my friend, because if you get hooked you're in for a wild ride!