Picks are a tool category with many uses! Picks tend to be available in sets because they are most useful when the appropriate shape (and size) is available. Most picks will be made out of metal but will sometimes be available in other materials, especially plastic, for when a non-marring tool is needed to prevent damage on whatever is being worked on.
Pick sizes vary; larger picks won't be able to get into tight spaces like the smaller ones can, but are more durable and able to pry on stronger objects.
Different pick shapes help perform particular tasks, but some tasks can be performed by multiple shapes. Having a variety of pick types on hand tends to make jobs that require picks easier.
90° Hook Pick
A 90° hook pick can be used to reach under items when having a 90 degree offset handle is ideal. The angle also makes for a good general purpose pick when any angle will do. While this can be used for light prying, it generally isn't recommended for any prying where force is required.
Other angles are sometimes available, but a right angle is the most commonly available angle aside from straight.
Full Hook Pick
A full hook style pick makes for a great took for picking up something in a hard-to-reach place. The pointy end allows for picking up something as small as a thread, and the round end allows for easy holding of the item once the pick has grabbed it.
Cotter Pin Puller
While a 90° pick can be used for removing some cotter pins, the dual-offset of a cotter pin puller allows for multiple methods of extracting a cotter pin.
A cotter pin being used to lock a castle nut into place may be pulled out with this tool in a number of ways, all of which begin by putting the top through the eye of the cotter pin. If just pulling straight out doesn't work, the double offset allows rotation to convert into some pulling force when the shaft is held in place with a solid object. The double offset also allows for more than one prying leverage point, but this method may damage some cotter pin pullers when too much force is applied to particularly stubborn pins.
Straight Pick
The most basic type of pick, but quite easy to use. Sometimes when a straight pick is ideal for the job, a small flat-head screwdriver is used instead due to their abundance (and they are typically easy to find in a tool box as they are given priority) but there are some jobs where a true straight pick has no replacement. Inversely, sometimes the screwdriver is actually the better tool for the job!
Hose Puller
A hose puller pick is designed to get between the hose and the inlet/outlet it gets sealed to. The pick gets moved around between the two components to break loose the bond that typically forms between them, especially when corrosion is involved.
Care should be taken if the hose is to be re-used, because a hose pick can damage the hose. However, there may be situations where the damage is inevitable.
The hose puller tool tends to be most effective on larger diameter hoses such as radiator hoses. It can sometimes do the job on smaller hoses, but it's more likely to split a hose the smaller the inside diameter of the hose gets. For very small hoses like many vacuum lines, a 90 degree pick.
Offset Hook
The offset hook is similar to the cotter pin puller, but is smaller and great at removing O-rings. The offset close to the tip allows for an easy rotating motion to get under an O-ring and pull it up.
The offset also helps in situations where something needs to be scraped inside a small hole, such as removing threadlocker residue from inside diameter fastener threads.
Awl
A stronger version of the straight pick. Awls are often used in woodworking and leather work, but it may find occasional use in the automotive repair setting. Awls are often used to push holes into softer materials.
An awl can sometimes be used to loosen up a hose, but the hose puller's angles make it the better choice for that in most instances.
Non-Marring Picks
Non-marring picks are typically made out of fiberglass-reinforced nylon or similar plastic, and is an intentionally weak choice to prevent damage to the object being worked on.
Similar to trim panel removal tools, the plastic is typically soft enough to give way before too much force damages the item being worked with.
Hook & Pick Safety
The sharp ends of picks/hooks can easily puncture skin, so care must be taken to avoid using the tool where it may come in contact with skin. Thick gloves and safety goggles may help, but situations may present themselves where those are insufficient protection. Always read the safety instructions included with your tools, as this section does not cover the full extent of safety requirements.