Sneak (Fallout: New Vegas)

Sneak is a skill $$ It determines the chance of being detected while sneaking.

Initial level
\text{Initial level}=2+(2\times\text{Agility})+\left\lceil\frac{\text{Luck}}{2}\right\rceil Example: A starting Agility of 5 and Luck of 5. 2+(2\times5)+\left\lceil\frac{5}{2}\right\rceil=15

Improving

 * Permanent
 * Leveling up (up to 10 + INT/2 + 2 with Educated perk)
 * Chinese Army: Special Ops Training Manual (+3 or +4 with Comprehension perk)
 * Agility Implant (+1 depending on current Agility, a perfect Agility of 10 will see no benefit)
 * Tag! (+15)
 * Skilled (+5)
 * Temporary
 * Fire Ant Nectar (+2-8 depending on current Agility, a perfect Agility of 10 will see no benefit.)
 * Recon armor (+5)
 * Stealth Boy (+100, +75 cloaking field)
 * Chinese Stealth Armor (+5)
 * ¡La Fantoma! (+10 or +20 with Comprehension perk)
 * Assassin suit (+10)
 * Salt-Upon-Wounds' helmet (+5)
 * Stealth Suit Mk II (+15 or +25 with the Firmware 1.1 Upgrade)
 * Dead Horses stalker armor (+5)
 * Blood-Nap (+10)