In Left 4 Dead, you can't give your medkit to anyone else, you can only use it on them. This leads to amusing animations where the survivors wrap each other in bandages while tossing out a few lines of dialog. I have to admit that when I was new at the game, I wasn't crazy about getting all touchy-feely with Mr. Big and Greasy Francis the biker.
If Valve tracked it, I would love to know if Zoey gets healed more often than the other characters overall. I doubt it's much, but I wouldn't be at all surprised to find out she gets healed 5% more often than the men.
Shamus Young is a programmer and writer by trade, videogame nitpicker by inclination. If you have the patience for more of his ramblings, they can be found at ShamusYoung.com.