Feel free to comment any new console commands that work below and feel free to test any that I haven't (but at your own risk). :D

These console commands have the potential to break your game so don't hold me responsible for that!

Manually set a stage in a quest to complete buggy objectives:
For example: "setstage MQ08Prologue 45"

Find out all stages of a quest:
For example: "player.sqs MQ08Prologue"

Change FOV:
Changes field of vision without need of opening options.

Disable all UI:
Toggles on and off all UI. Useful for screenshots.

Clear blood effects from screen:
Clears all blood effects on players screen.

No clip mode:
Toggles on and off no clip mode so you can phase through objects.

Timescale:
For example, "set timescale to 10" means every real life minute will mean 10 in-game minutes will pass.

Set time:
For example, "set gamehour to 0800" sets time to 8 AM.

See characters inventory:

Disable grass:
Toggles on and off grass.

Disable trees:
Toggles on and off trees.

Disable water:
Toggles on and off water.

Reset a characters inventory:
Restores the target's inventory to its original state.

Change sex of your character:
Changes the sex of your character (only body).

Place NPCs or enemies or items at player:
Places items or NPCs next to the player.

Set player size:
Makes the player bigger or smaller. I believe 1 is default size(?)

Add any item (you will need item codes):

Add coins:

Add lockpicks:

Remove an NPCs items:
You have to click on the NPC after bringing up the console.

Increase health, stamina and/or mana:
For example, "player.setav health 1500" sets your health to 1500.

Increase Carry Weight:

Memory points:

Crafting points:

Player level:

Player speed:
For example, "player.setav speedmult 200" is double normal speed.

God mode:
Toggles god mode on and off.

Unlock all map markers:
Toggles all map markers. 1 unlocks all map markers and 0 hides all map markers.

Unlock all spells:

Make NPC's immortal:
1 means immortal, 0 makes them killable. NOT TESTED YET

Make followers/NPCs immune to damage and staggering:
Click on the NPC you want to make immune to damage and staggering. 1 means immune and 0 means they take damage. NOT TESTED YET

Toggle on and off AI:
Toggles off all AI, freezing everyone. NOT TESTED YET

Toggle on and off hostile AI:
Toggles off all hostile AI. NOT TESTED YET

Kill an enemy or NPC:
Need to click on the NPC after opening console.

Resurrect an NPC:
Need to click on the NPC after opening console.

Unlock locked doors and chests and lock them:
Need to click on the object first.

Main command:
E.g. "player.additem 149676 1" adds a single Memory book to add one skill point to the character.

How to find item codes:

Useful item IDs:

Learning books:
149676 - Learning Book +1 Memory Point
CE135 - Learning Book: +2 Learning Points

While I don't really use console commands I felt it would be helpful for those of you who do to create this guide. The main reason I made this was because one of my quests broke and I had to set stage using console commands to fix it, so hopefully this can help others, but over fun, console commands are also included as I might as well make a complete list.