I've been caught weak by just about every story mentioned in this thread so far. Car broke down with kids (in my case it was grandkids, and I gave the man my jumper cables, 5 cigarettes, and the whole $1.62 in my wallet), a woman trying to get "home." Once I even "loaned" a woman $80 for a tow truck. Oh yea, I'm a sucker for a sob story; maybe because I've been the subject of a few (though never enough to ask strangers for money). I also pledge to most of the Police/Fire/EMT solicitors that call, although that is seeding, so a different situation.
I've also been out of it enough to have a similar experience as the one wth the creamer caraffe, and stretching across to hold the door. Oh yea, I have my moments.
As to the smartass who was nervy enough to ask for more than you gave... at that point I may very well have taken the dollar back and walked away. Asking is one thing - demanding is another. Bitch.