Caffeine (look it up), in my book. Both are alkaloids, but nicotine is
much more toxic and much more addictive. One develops tolerance to both,
though since I haven't tried nicotine I don't know how fast that one comes
on.
BTW, I'm assuming you're contemplating something like a patch. Smoking
speeds nicotine out of the realm of "unwise", passes through "entropic"
without slowing down, and comes to rest somewhere downstream of "damned
stupid". That inteligence and will are largely unrelated is the only
explanation I can find for those of my (undeniably intelligent) friends
who haven't been able to beat that monkey off their backs yet.
Personally, I tend to avoid caffeine except in cases of emergency, too
(I narrowly avoided a chocolate-covered espresso bean habit), just
because of the tolerance effect. I want it to work when I need it.
Incidentally, you might get more interesting answers from "What's a
[legal, nonaddictive, powerful, fast-acting, nonprescription, cheap,
whatever your constraints are] nootropic?".
Cheers,
Kennita
Kennita Watson | The bond that links your true family is not one of blood,
kwatson@netcom.com| but of respect and joy in each other's life. Rarely do
| members of the same family grow up under the same roof.
| -- Richard Bach, _Illusions_