Bill, AA alkalines are at 1.5V, 14500s at 3.7V nominal. Which means, if you put a 14500 in a AA light that was meant for alkalines only, you'll probably fry the light. So, as Str8stroke said, we need to know exactly what lights you're talking about, so we can tell you which can and can't handle the greater voltage of 14500s (or, if you can find manuals on the web, look to see if the manual says your light can handle voltages up to 4.2V). If the point is that you want to move to rechargeables, any light that can run on AA alkalines can also run on AA Eneloops, so it's not like 14500s where have have to worry about frying a light. Are you aware that 14500s (at least LiCo) are an unsafe chemistry and need a little bit of special handling? If not, you shouldn't even be thinking about them, a vent-with-flame event in a flashlight (think mini pipe bomb) would be no fun at all. Eneloops are rechargeable and safe, and are definitely safe in all your current alkaline AA lights, and will not vent with flame. I run just about everything in my house on Eneloops: remote controls, flashlights, etc.
My guess is, someone who is so new that they don't even know how to tell if their lights can handle 14500, also doesn't understand the care and feeding guidelines for unsafe battery chemistries, and should definitely be thinking Eneloops. If you were my best buddy and we were talking, that's what I'd tell you. Then sometime down the line, when you've educated yourself on the care & feeding guidelines (and risks!), you can move over to 14500s in lights that can handle it ... and by then, you won't need to ask us which lights, you'll understand.
