The Elder Scrolls IV: Oblivion/Stealth Skills

Acrobatics
The simple act of jumping, combined with other actions. Anybody can jump, naturally, but skilled Acrobats can jump higher, take less damage when falling from high places, attack in mid-air, and even dodge enemies' attacks with ease.

Alchemy
The art of making ordinary plants and meats into potions capable of bestowing magic effects. To use Alchemy, you need at least a mortar and pestle (there is one sitting on a crate during the tutorial sequence in the beginning of the game). Equip the mortar and pestle in your inventory to open the Alchemy window. To create potions, you need to find two different ingredients with the same effect. You can add up to four ingredients (for up to 3 different effects for a single potion, for Apprentice level and up). As your skill increases, ingredients have more potential effects that you may harness.

Alteration
One of the branches of magic that can be used. Alteration is the ability to modify the very physics of the universe. With Alteration spells, you can create magical shields on yourself and others, burden others, or lighten your own load so you can carry more items without becoming over-encumbered. You can also unlock doors from a distance with the proper spells.

Armorer
An Armorer can repair weapons and armor to maximize their effectiveness. You need a Repair Hammer to use this skill. Journeyman Armorers can repair enchanted weapons and armor, and more experienced Armorers can also repair Daedric weapons.

Athletics
Athletics affects how fast you can run on land, how fast you can swim in water, how long you can hold your breath, and how fast your Fatigue regenerates.

Conjuration
A Conjurer has the ability to summon monsters and Daedra from thin air to do their bidding, in addition to creating bound armor and weapons to use in battle.

Destruction
Magical self-defense, in the form of fireballs, electric blasts, or balls of ice. Most Mages would do well in building this skill, while others could use it as a secondary means of defense when one's Fatigue is too low to fight.

Hand To Hand
The ability to fight and kill foes with nothing but one's own hands. While not as powerful as using a weapon (and certainly not as good to block with), hand to hand combat is fast and doesn't use as much fatigue. Higher skill levels give you more power attacks which can be used to paralyze and disarm opponents.

Illusion
Skilled Illusionists can modify the way humans percieve reality - casting light, becoming invisible, or charming others into believing that you are a friend.

Marksman
The use of a bow and arrows to attack from a distance. Skilled Marksmen can do more damage, and truly gifted Marksmen also have the ability to zoom in while using a bow.

Mysticism
This branch of magic can be used to detect living creatures through walls, trap souls within soul gems, and levitate items across the room with telekinesis.

Security
When one is trained in Security, they understand all kinds of mechanical locks and traps. The higher your Security skill, the slower the pins will move in the lockpicking interface (or the better chance you will have of opening a lock using Auto Attempt).

Sneak
The talent of disappearing into the shadows without aid of magic, to pass behind foes without making a noise, and to deal insane amounts of damage by taking an opponent unawares. As your Sneak skill increases, the volume of your footsteps is dramatically lowered, your critical damage multiplier is increased, and sneak attacks will eventually completely ignore whatever armor your opponent is wearing.

Speechcraft
The use of words to convince others to aid you. As your skill increases, people will have a better initial reaction to you, and be more likely to respond positively when persuaded. If you lack Speechcraft skill, you can obtain similar effects by bribing the person in question.