I don't think an 8 is all that useful of a tool. I come from a background of many roped disciplines (rock climbing, caving, industrial access, caving, canyoning) and got started when I was a young teen. The 8 was the only thing I could afford, and it has a bunch of uses sure. You can rig them backwards for extra friction. But it's big, bulky and heavy, and it twists your rope. Locking it off is a pain.
For a simple descent tool, It's hard to go past a sticht plate/ATC/pigs nose etc. They weigh nothing, you can use them to descend single or double rope, they're cheap, and the ride is nice.
A gri gri is not a bad tool either, and you can use it for a bunch of purposes. You can setup a z link ascending system with one, use it for rescue lower off, use it to descend (it locks), and you can even use it for light in tree rigging, or as a secondary rigging point with a floating rig.
There are a bunch of specialised tools out there... racks, whales tails, 8's, gri gris, sticht plates, etc etc... I own most of them, but I just use a hitch cord. Who needs to carry all that stuff?
Shaun