I think they
could be used for multiple 5mm LEDs in series, rather than the usual parallel connection. Unfortunately, you'd be limited to 3 white LEDs, and they'd probably not be very bright (I don't really know about the resistance of coin cells/A23s, but it's not low), but would be fairly uniform, unlike many cheap multi-LED keychain lights, which have quite visible brightness variations among the parallel LEDs.
Peak has some tiny
keychain lights (pics w/ batteries in second post) for 10180 and 10280 cells, and Modamag has the
Draco for 10280. The 10280 would be
mechanically compatible with A23. I doubt an A23 can push enough current to blow anything, but I definitely wouldn't risk it unless the manufacturers approve. (The more so since it's quite a senseless decision...)
See, you're much better off with a single 10280 LiCo (which is
available with capacity of 200mAh = ~0.74Wh, not sure what discharge rate) than the A23. From Energizer's
datasheet, the A23 gets 39-55 mAh at a pathetically low
0.01C discharge, depending on cutoff voltage. Assuming a "working voltage" of 10V, and using the 6V cutoff, this is ~0.55Wh max (at ~0.5mA current!), so you're getting way less light out of a $2 primary than you would from a $5 rechargeable of the same size.
That's why nobody uses it.
If you
really must have 12V (at full charge) in a small package, which you shouldn't (unless you're making a small hotwire?!), modding a AAA light with 3x10180 is your best bet. It's a little larger than A23, but inordinately more energy and power. Now, when AW produces some IMR10100 cells, you could connect three of those in series for a high-current A23, and try for a Solitaire85 -- estimated runtime, 10 whole seconds!