It's a little lame to review a guitar pick, I know. But much as a painter will select different brushes for specific purposes (certain textures, sizes, whatever) a good guitarist should probably have a handful of picks available for specific tasks.
This floppy little Tortex plectrum is my go-to when strumming chords on an acoustic guitar. It's virtually useless for anything else--try playing electric, and you'll likely tear it in half on the strings halfway through one song. It's borderline awful for picking single notes, especially if you're going to play more than one per measure. It's too soft to snap back into position, and it's very easy to find yourself missing beats.
But let's go back to the acoustic strumming. If you've got a solid rhythm and a light-to-medium strumming technique, you'll find that one of life's most sublime pleasures is raking this paper-thin pick across a fresh set of bronze strings. There's just something so clean about the sound this plectrum draws from a guitar; it sounds like all the great background rhythm playing on classic rock records from Bowie's 70s stuff to the Who's... well, almost everything.
The red tortex picks were my favorites when I was in highschool. I played in Jazz Band and I must have gone with really light, floppy picks to be contrary. Its very un-jazz to use a pick less than 1mm. The thin tortexes last a long time and have good flex for certain kinds of speedy runs. They sound very good on acoustic. I am not picky anymore, I use whatever is handy (often my hands are handiest), but I used to give a shit and I liked these. I do not know why. They're not special nor are they especially awful...
I know I still have a bunch in one of my cases.