Picks

Guitar pick is a type of plectrum designed for use on a guitar. Over time people have made picks of various materials, including nylon, plastic, rubber, felt, tortoiseshell, wood, metal, and stone. The most often take the shape of an acute isosceles triangle with the two equal corners very rounded and the third corner rounded to a lesser extent. This shape is, however, merely one of many used by manufacturers.
Guitar picks come in varying thickness to accommodate the different playing styles and kinds of strings. Thinner plectra are more flexible and tend to offer a wider range of sounds, from soft to loud, and produce a "click" that emphasizes the attack of the picking. However, some argue that heavier picks produce a brighter tone.

Picks will normally have small protrusions to make them easier to keep hold of if the fingers start to sweat. Some picks will have a high-friction coating to help the player hold on to them. The small perforations in the stainless steel pick serve the same function. Many players will often have spare picks attached to a microphone stand or slotted in the guitar's pickguard.
Picks made out of steel will produce a much brighter sound than plastic ones. They do however wear the strings quickly and can easily damage the finish on the guitar if used for strumming - especially on acoustic guitars.

The equilateral pick can often be much easier for beginners to hold.
The shark's fin pick can be used in two ways - normally employing the blunt end or the small perturbations can be raked across the strings producing a much fuller chord.