Class abilities may be available through feats. This means you could further your Specialist powers as a Wizard/Assassin or pick up Favored Enemy as a Fighter.
Bed of Iron is now a Transmutation spell.
Dex can be applied to melee damage in place of Strength with the new “Deadly Expertise” feat (prereq: Weapon Finesse).
Undead can be animated with templates, but each template doubles the effective HD of the creature for the purposes of animation.
Additional attacks can be made with any weapon (so long as the preparation for the next attack is a free action) by applying a cumulative -4 to all attacks made. In essence, everyone has a shittier Rapid Shot, and it even applies to melee. These additional attacks cannot critically threat nor confirm, and this can only be done when making a full-attack action.
In that same area of thought, melee characters may be interested in taking the “Rapid Strike” feat (prereqs: Str or Dex 13, BAB +2) that allows a melee-user to make an additional melee attack by taking a -2 penalty to all attack rolls that round during a full-attack action.
The Power Word spells (Power Word Kill, etc) do not need to be prepared from a Spellbook.
Wizards cannot cast spells from their opposed schools. The “Opposition Research” discovery can allow a Wizard to cast and use opposition spells from one school with their normal penalties. Taking the discovery again and selecting the same school can allow you to use the school’s spells to full effect. In addition, this discovery is available starting at 5th level rather than 10th.
Spellcasters receive one less spell slot per level. If this reduces the spell slots to “0”, then spells of that level cannot yet be cast, regardless of your appropriate casting modifier.
The “Mystic Theurge” prestige class requires only 2 levels of Arcane and 2 levels of Divine casters, making it obtainable by 5th level. It still requires 3 ranks in Knowledge (Arcana) and (Religion). In addition, the MT gets 4+INT mod skill ranks, as opposed to 2, and adds Use Magic Device to their skill list.
Monks get higher unarmed damage one level later than usual (including 1st), but still get 2d10 at level 20.
Unless otherwise stated, your ability scores are determined by rolling 4d6, rerolling 1s, and dropping the lowest. If you did not get any 18s, you can replace your second-highest rolled ability with an 18.
The Stunning Fist feat has been replaced by Stunning Strike. It has the following prereqs: Wis 13, BAB +9, Proficiency with the selected weapon. The feat applies to a weapon chosen by the player when the feat is gained.
Alignment restrictions on classes are removed but still encouraged.