Realistically, you can't really get much of a pick-me-up in something the size of a tablet, except maybe caffeine. And even that doesn't seem to work all that well. It prevents sleep sometimes, but doesn't really make you alert.
Amphetamines, like the aforementioned Benzedrine, reportedly do a hell of a job perking you up (no personal experience though <img src="/images/graemlins/grin.gif" alt="" />). However, I wouldn't want anyone going to jail because of the contents of their survival kit.