While in Brazil I picked up a repique de anel, an instrument that for whatever reason doesn't seem to get played as much as it used to, which is a real shame, because it's a lot of fun and a great sound, particularly in samba. I had been wanting one for awhile anyway, and then ended up spending some time talking about it in my lesson with Kiko Freitas.
It was invented by a man named "Dotô" or "Doutor to Repique". As best as I can tell he took a regular samba repique, tuned it down, and played it with his hands, the idea being that he could create a full samba sound with this instrument alone. The only picture I've been able to find of him is a grainy shot from a video of him playing with Clara Nunes.
With one hand on the underside of the drum he uses a dead stroke to play the heartbeat rhythm that is most commonly played on the bass drum in samba drumset playing. He also uses open sounds for fills and variations in conjunction with the other hand (more on that in a moment). With his other hand he taps the side of the shell much like one would on a tantan or repique de mão. However, Dotô gets a more metallic sound by putting "rings" on his fingers. "Anel" is Portuguese for "ring", so the instrument name literally translates to "repique of the rings", but from what I've seen it appears to be more like thimbles on his finger tips. Nowadays players often tape coins to the side of the drum so that one doesn't have to remember their rings. Here he plays a telecoteco-ish pattern with some extra notes added, presumably to fill out the bar. With the same hand as the rings Dotô uses his thumb to play variations and fills on the top head.
What you end up with is a groove that looks like this: