I pinch it together with my thumb and I have something that means "that is perfect and I don't need to tell you anything else." I stick it away from my middle finger and I flash a peace sign and wag it over my head as I walk away from a friend, craning my neck around to flash a quick goodbye smile.
Some time ago I used my index finger to manipulate my mouse on an IBM thinkpad laptop. A shooting pain started to extend its way all the way up my arm while I worked that little red dot in the middle of the keyboard. Today I have an ergonomic mouse (and keyboard, and chair, and desk), so that's been an improvement indeed.
My index finger is for scooping up the last bit of pasta sauce from the bowl, after the pasta had its turn swirling around. It's for scraping chocolate frosting off the side of the 13x9 clear Pyrex tray that my mom uses to make birthday cakes.
When I dance, I often put my head down, move my arms a lot at a 90 degree angle, and stick both of my index fingers up. If that sounds strange, that's because it is. It really is.
My laptop endured a Nalgene-induced deluge 5 years ago in the midst of hammering away at a Poli Sci midterm on my laptop. I'm surprised it has pulled through all these years, but it is now showing signs of its age. I can't use my right index finger to tap any of the keys in the very top row. It doesn't want to adjust its volume, the screen brightness, or to skip forward in a video. My computer is old, crotchety. It is there to stay.
I use my right index finger to decide where to go next on a hike when I come to a fork in the road. I lick my finger and stick it up in the air as if I know which way the wind is blowing. "Let's go that way," I say, not authoritatively at all.
It's for a stretched out woven silver ring that is too big for any other finger. Still, I worry some day it will slip off in a sink and the drain will take it away.