I haven't done one of these before here, but they've been popular in the past and are even useful in the future when found via search engines.
These changes can help you get an idea of the type of things Blizzard is doing internally.
Global API Functions: New
- AntiAliasingSupported
- BuyReagentBank
- C_Garrison.CancelConstruction
- C_Garrison.CastSpellOnFollower
- C_Garrison.CloseGarrisonTradeskillNPC
- C_Garrison.CloseRecruitmentNPC
- C_Garrison.GetAvailableMissions
- C_Garrison.GetAvailableRecruits
- C_Garrison.GetBuffedFollowersForMission
- C_Garrison.GetInProgressMissions
- C_Garrison.GetLandingPageItems
- C_Garrison.GetOwnedBuildingInfoAbbrev(plotInstanceID)
- C_Garrison.GetPossibleFollowersForBuilding(plotInstanceID)
- C_Garrison.GetRecruitmentPreferences
- C_Garrison.GetSpecChangeCost
- C_Garrison.IsUsingPartyGarrison
- C_Garrison.RecruitFollower
- C_Garrison.SetRecruitmentPreferences
- C_Garrison.SetUsingPartyGarrison
- C_LFGList.ApplyToGroup
- C_LFGList.CancelApplication
- C_LFGList.ClearSearchResults
- C_LFGList.GetApplicationInfo
- C_LFGList.GetApplications
- C_LFGList.GetAvailableRoles
- C_LFGList.GetSearchResultFriends
- C_LFGList.GetSearchResultInfo
- C_LFGList.GetSearchResults
- C_LFGList.Search
- C_ToyBox.ClearAllSourceTypesFiltered
- C_ToyBox.FilterToys
- C_ToyBox.GetFilterCollected
- C_ToyBox.GetFilterUncollected
- C_ToyBox.GetIsFavorite
- C_ToyBox.GetNumFilteredToys
- C_ToyBox.GetNumLearnedDisplayedToys
- C_ToyBox.GetNumTotalDisplayedToys
- C_ToyBox.GetNumToys
- C_ToyBox.GetToyFromIndex
- C_ToyBox.GetToyInfo
- C_ToyBox.GetToyLink
- C_ToyBox.IsSourceTypeFiltered
- C_ToyBox.PickupToyBoxItem
- C_ToyBox.SetAllSourceTypesFiltered
- C_ToyBox.SetFilterCollected
- C_ToyBox.SetFilterSourceType
- C_ToyBox.SetFilterString
- C_ToyBox.SetFilterUncollected
- C_ToyBox.SetIsFavorite
- DepositReagentBank
- GetCurrentLevelDraenorTalent
- GetLootInfo
- GetReagentBankCost
- GetSpellsForCharacterUpgradeTier
- HasDraenorZoneAbility
- HaveQuestData
- IsArenaSkirmish
- IsPlayerInMicroDungeon
- IsQuestSequenced
- IsReagentBankUnlocked
- JoinSkirmish
- MonumentChangeAppearanceToTrophyID(trophyID)
- MonumentGetSelectedTrophyID
- MonumentGetTrophyInfoByIndex
- MonumentLoadSelectedTrophyID
- MonumentRevertAppearanceToSaved
- MonumentSaveSelection
- ReagentBankButtonIDToInvSlotID(buttonID)
- RequeueSkirmish
- SortReagentBankBags
Global API Functions: Removed from 18179
- BNGetFriendInviteInfoByAddon
- C_Garrison.GetActivatableBuildings
- C_Garrison.GetBuildingActivationInfo
- C_Garrison.GetLandingPageMissions
- C_Garrison.GetMissions
- MonumentGetTrophyIDByIndex
- MonumentReplaceWithTrophyID
- RequestQuestData
Global API Functions: Removed from MoP
- GetExistingLocales
FrameXML Functions: New
- C_Timer.NewTicker
- C_Timer.NewTimer
- ReagentButtonInventorySlot
- ShowQuestLog
- ToggleWorldMap
Events: New
- ACTIONBAR_SHOW_BOTTOMLEFT
- CHARACTER_UPGRADE_SPELL_TIER_SET
- CHAR_RESTORE_COMPLETE
- GARRISON_HIDE_LANDING_PAGE
- GARRISON_MISSION_BONUS_ROLL_LOOT
- GARRISON_MONUMENT_SELECTED_TROPHY_ID_LOADED
- GARRISON_RECRUITMENT_FOLLOWERS_REFRESHED
- GARRISON_RECRUITMENT_NPC_CLOSED
- GARRISON_RECRUITMENT_NPC_OPENED
- GARRISON_RECRUIT_FOLLOWER_RESULT
- GARRISON_SHOW_LANDING_PAGE
- GARRISON_TRADESKILL_NPC_CLOSED
- GARRISON_USE_PARTY_GARRISON_CHANGED
- HEIRLOOMS_UPDATED
- LFG_LIST_SEARCH_FAILED
- LFG_LIST_SEARCH_RESULTS_RECEIVED
- LFG_LIST_SEARCH_RESULT_UPDATED
- LFG_ROLE_CHECK_DECLINED
- LOOT_READY
- PLAYERREAGENTBANKSLOTS_CHANGED
- PLAYER_AVG_ITEM_LEVEL_UPDATE
- QUESTLINE_UPDATE
- QUEST_CHOICE_CLOSE
- QUEST_TURNED_IN
- REAGENTBANK_PURCHASED
- REAGENTBANK_UPDATE
- SCENARIO_COMPLETED
- TOYS_UPDATED
Events: Removed from 18179
- ASSIGN_FOLLOWER_TO_BUILDING_RESULT
- CHAR_RESTORE_COMPLETE
- QUESTLINE_UPDATE
- REMOVE_FOLLOWER_FROM_BUILDING_RESULT
Events: Removed from MoP
- PLAYER_AVG_ITEM_LEVEL_READY
Widget API: New
- Cooldown:SetCooldownDuration
- Cooldown:SetHideCountdownNumbers
- GameTooltip:SetMountBySpellID
- GameTooltip:SetToyByItemID
- SimpleHTML:GetContentHeight
Widget API: Removed from 18179
- GameTooltip:SetMountBySpellID
- GameTooltip:SetToyByItemID
Widget Handlers: Removed from 18179
- Browser OnButtonUpdate
- Browser OnError
- Browser OnExternalLink
- EditBox OnArrowPressed
- GameTooltip OnTooltipSetEquipmentSet
- GameTooltip OnTooltipSetFrameStack
Lua Enums: New and Updated
- [[LE_FRAME_TUTORIAL]]
- _GARRISON_BUILDING = 9 (new)
- _GARRISON_MISSION_LIST = 10 (new)
- _GARRISON_MISSION_PAGE = 11 (new)
- _GARRISON_LANDING = 12 (new)
- [[LE_ITEM_QUALITY]] (new)
- _POOR = 0
- _COMMON = 1
- _UNCOMMON = 2
- _RARE = 3
- _EPIC = 4
- _LEGENDARY = 5
- _HEIRLOOM = 7
- [[LE_UNIT_STAT]] (new)
- _STRENGTH = 1
- _AGILITY = 2
- _STAMINA = 3
- _INTELLECT = 4
- _SPIRIT = 5
Check out Patch 6.0.1 API Changes on Wowpedia for a full list of changes since Mists of Pandaria!