Scrolls are represented by ? and have a weight of 5. Each one has a different effect when you read it, some effects highly desirable, some not. Most of them are useful in some way, and this page isn't comprehensive by any means. Be creative!
You may want to read about scrolls first.
Always useful scrolls
Scrolls of enchant weapon are common, useful, and easy to price ID, with their unique base price of 60. Like most scrolls, they're better used when blessed, but the player's immediate survival is often much more important than hoarding resources for a future that might not come. Don't be afraid of "wasting" these before getting an artifact weapon or holy water. Weapons enchanted above +5 have a substantial chance of evaporating if you attempt to enchant them further.
The scroll of enchant armor is one of the most valuable scrolls in the game. Better AC greatly reduces damage to the player and is one of the primary factors that influence player progression. Even without a powerful weapon, a player with a very good AC can last for quite a while. Early in the game, they're best used on items that you'll likely keep, such as any gloves or helm, or any magical armor such as a cloak of magic resistance or speed boots. If the player lacks magic resistance or polymorph control, it is not advised to enchant items in the shirt, body armor, or cloak slot, as these can be destroyed if the player is unfortunate enough to step on a polymorph trap. Fortunately, like enchant weapon, enchant armor is very easy to price identify, only sharing its base cost of 80 with remove curse, a scroll that is also safe to read identify. Be sure to curse-test both this and the enchant weapon scroll before reading, though.
A scroll of charging is especially handy to have around. Maybe you want to recharge your magic marker or wand of death, unless the scroll is cursed, you can recharge it. Some objects explode after experiencing the charging process too many times, so be careful. These scrolls are rare, so save the ones you have. They are relatively cheap to write for their utility, however, so consider using magic marker charges on them.
The scroll of teleportation is a good escape item, particularly in the early game where most levels do not prohibit teleporting. Cursed scrolls can be convenient if the player doesn't have another means of level teleportation or branchporting. They're extremely common as a defensive item that monsters are eligible to carry, so most of them can be blanked. Monsters are likely to identify this scroll for you early on.
The scroll of genocide is very powerful, and how you choose to use it depends on its BUC status. See genocide. It has potential utility at any point in the game, and can be used as an escape item, to produce dragons for their dragon scale mail, or to wipe out entire classes of powerful monsters. Although its base scroll class of 300 can be very dangerous, all of them can be safely read identified if they are blessed.
A scroll of scare monster is a powerful item indeed. Unlike most scrolls, its most powerful effect occurs when it is dropped, scaring all monsters except for A and the Riders. After the Elbereth nerf that occurred in 3.6.0, these can save your life against anything from killer bees to Demogorgon. It's a good idea to have one in a container that you can #tip in an emergency. There is a guaranteed scroll under the Sokoban prize. Although it is cursed, and will crumble when you pick it up, it allows you to identify them easily.
Useful early- and mid-game scrolls
Scrolls of identify should be kept and used. Even if they are cursed, they still allow you to identify one item, and identifying items can show you the enchantment, identity, and BUC status of the item. They are the cheapest scroll, and are usually easily discernible due to their frequency in generation. Use them to identify items that are difficult to identify safely or discern from others in their price ranges, such as rings and amulets.
The scroll of remove curse can be used to remove curses on wielded and worn items if it is uncursed, uncursing the player's entire inventory when blessed. They see use in removing curses in otherwise useful armor and rings, and uncursing accidentally worn items or loot from bones files. Later in the game, they can be used to create unholy water or to mitigate the effect of curse items.
Although it can be difficult to identify due to its common base price of 100, the scroll of confuse monster can be used in a pinch to attempt to confuse an attacker. It becomes far less useful later, serving only as a source of confusion for the player should they need it.
A scroll of taming is rare and difficult to identify as well, but many earlygame monsters lack good monster MR, making them vulnerable to taming's charm monster effect. This can be used to get moderately powerful pets or just to escape a sticky situation.
Scrolls with specialized uses
Many players rely on the scroll of magic mapping in Gehennom. Manually exploring Gehennom is a chore that most players choose to streamline, although this is strictly a luxury and shouldn't be prioritized. Earlier in the game, their main usage is to navigate dark levels in the Gnomish Mines or to locate vaults more easily.
While near useless in the early game, the scroll of gold detection is valuable on the Elemental Planes to locate portals.
The scroll of destroy armor has some uses. If you are wearing cursed armor without a scroll of remove curse, you could drop all your other armor and read the scroll (this will not work if the scroll is cursed, it will lower the enchantment of the armor instead), destroying the armor. Later in the game, cursed scrolls of destroy armor can be used to fooproof armor if read when confused.
Scrolls to blank
The scroll of light may see marginal use at the very beginning of the game, but is otherwise worthless. Its effect is easily superseded by any source of light, such as oil lamps, the wand of light, or candles. It is easy to identify and type name due to its unique base price of 50.
Unless you are pursuing some esoteric stupid ascension trick, the scroll of punishment is also a prime candidate for blanking.