General Rules not Allowed: Called Shots, Massive Damage, Alternate Favored Class Bonuses, Alternate Racial Traits (for exceptions see Additional Traits), Monk vows, Paladin oaths, Hero point feats, hero point items and hero point spells, Story feats, Daring Acts and similar roleplay-based trade-offs.
Customization: You cannot customize your own class features, archetypes, feats or spells (such as the methods from the ACG).
Gunslinger: DEX mod to damage does not stack with itself (see archetypes).
Summoner: (Synthesist) archetype.
Third Party: No third party material of any type (including all psionics).
Dimensional pockets: Examples include mage's sanctum, rope trick or bags of holding).
Permanency: Permanent spells, SLAs, SNAs, and other effects that last more than 24 hours (such as Permanency), including those that say "instantaneous" but create something permanent (such as Animate Dead) and items that utilize these effects do not function outside the arena, nor can their created effects be brought into the arena. All such effects must be cast or created during combat to be utilized.
Spell Mimicry: Spells, SLAs and SNAs that mimic other spells (such as Wish, Miracle or Shadow Conjuration). Greater or lesser versions of other spells are allowed as they don't count as "mimicking" because they are very specific. Also, class features and racial traits granting abilities that emulate banned spells (such as a Shadowdancer's) are still allowed.
Automatic Hits: Automatic success effects such as Magic Missile which always hits or Waves of Fatigue which allows no save or Power Word spells. All unwilling effects that target creatures and attended objects must have an attack roll, combat maneuver check, opposed skill check or saving throw which negates or reduces their effect. All effects creating conditions for an ongoing duration must allow a saving throw to half the duration (even if they already have an attack, CMB or skill check). Otherwise, they are banned. As the keyword "duration" notes, this does not apply to effects that have no duration or effects that are sustained such as combat maneuvers, feint, Stealth and similar checks. Ability damage/drain and level drain are treated as conditions for these purposes.

A character who has not yet acted during a combat is flat-footed, unable to react normally to the situation. A flat-footed character loses his Dexterity bonus to AC and Combat Maneuver Defense (CMD) (if any) and cannot make attacks of opportunity, unless he has the Combat Reflexes feat or Uncanny Dodge class ability.

Characters with Uncanny Dodge retain their Dexterity bonus to their AC and can make attacks of opportunity before they have acted in the first round of combat.

Squeezing

In some cases, you may have to squeeze into or through an area that isn't as wide as the space you take up. You can squeeze through or into a space that is at least half as wide as your normal space. Each move into or through a narrow space counts as if it were 2 squares, and while squeezed in a narrow space, you take a –4 penalty on attack rolls and a –4 penalty to AC.

When a Large creature (which normally takes up 4 squares) squeezes into a space that's 1 square wide, the creature's miniature figure occupies 2 squares, centered on the line between the 2 squares. For a bigger creature, center the creature likewise in the area it squeezes into.

A creature can squeeze past a creature while moving but it can't end its movement in an occupied square.

To squeeze through or into a space less than half your space's width, you must use the Escape Artist skill. You can't attack while using Escape Artist to squeeze through or into a narrow space, you take a –4 penalty to AC, and you lose any Dexterity bonus to AC.