Oblivion:Luck

Luck governs no skills directly, nor does it boost your skills over 100. However, it affects just about everything in the game. A luck value of 50 means that nothing goes for you or against you. Luck above 50 influences events in your favor. Luck below 50 influences events against you.

In-game Description: Luck has an effect on everything you do, but governs no skills.

Luck modifies all your skills (except Acrobatics, Athletics and Speechcraft) behind the scenes as follows:
 SkillModifiedByLuck = SkillInQuestion + ( ( fActorLuckSkillMult * Luck ) + iActorLuckSkillBase )
With default settings the formula goes as follows:
 SkillModifiedByLuck = SkillInQuestion + ( 0.4 * (Luck - 50 ) )
In other words, a skill is increased by 40% of however many points of Luck you have over 50; e.g., for a player with Luck of 60, influenced skills are increased by 4 (40% of 10) skill levels (skill points) and for a player with Luck of 100, influenced skills are increased by 20 (40% of 50).  These luck boosts do not grant the skill perks if the hidden bonus pushes you to the journeyman, expert etc. ranks. Luck increasing you armorer skill to master or above is an exception to this, however. If luck brings your armorer skill to master, your repair hammers will not break.

Fortifying luck past 100 continues to raise the modified skill values.  However, the modified skill value is constrained in the game's calculations to be in the range 0 to 100.  This modified value is not displayed in the Skills menu, but it is the value used for all game calculations (for example, damage done with a weapon or the magic cost of casting a spell).

In addition to modifying skill levels, Luck probably influences most situations where the game randomly determines events, such as a repair hammer or a lockpick breaking.  Confirming the role of luck in changing probability is difficult, because in most cases the details are hidden within the game engine.  However, there are a couple cases where scripts make use of the player's luck:
When betting in the Arena, your luck controls the initial health of the gladiators, improving your chance of winning.
Luck determines the chance that striking an opponent with Mehrunes Razor will result in Daedric Banishing.

Luck does not have any impact on what loot you will receive from containers or other leveled lists.

While every other attribute can be maximized quite easily with 10 or so levels of +5 attribute increases, it takes at least 35 levels (50 normally, 45 if Luck is a class attribute, 40 with The Thief birthsign and 35 if both the Thief Birthsign AND a custom class using Luck as a class attribute are used) of raises to maximize luck. See Leveling +5/+5/+5 vs +5/+5/+1 for more on how to do this.

Character Creation

All Races and genders start with an initial luck value of 50.  A luck rating of 50 is considered "Neutral" by the game's calculation, and luck lower than 50 will actually be detrimental.

An initial +10 luck bonus is possible by selecting The Thief as your birthsign.

No standard classes have luck as a class attribute (That is to say, you must create a custom class in order to gain a +5 bonus to it at character creation).

The maximum initial value of Luck is 65, which is only possible if you both choose The Thief as your birthsign and create a custom class with Luck as a class attribute.

See Also
Increasing Attributes: Information on how to increase luck.
Magic Items: There are multiple generic items that fortify the luck attribute.
Unique Items: A list of unique items, of which only one fortifies the luck attribute. These do not include Leveled Items such as those received from quests, or Artifacts.
::*Ring of Wortcraft is a unique ring that can be obtained from Falanu Hlaalu at the All Things Alchemical. Among other enchantments it fortifies your luck attribute by 5 points.