What are all the gamerule commands in Minecraft?

On the Command and Command Block page on the Minecraft Wiki, there are lists and tables describing the /gamerule command.

• commandBlockOutput - Whether command blocks should notify admins when they perform commands.
• doDaylightCycle - Toggles the day-night cycle (the sun stops moving and stays where it is) (added in 1.6.1)
• doEntityDrops - Whether entities that are not mobs should have drops.
• doFireTick - Whether fire should spread.
• doMobLoot - Whether mobs should drop items.
• doMobSpawning - Whether mobs should naturally spawn.
• doTileDrops - Whether blocks should have drops.
• keepInventory - Whether the player should keep items in their inventory if they die.
• logAdminCommands - Whether to log admin commands to server log
• mobGriefing - Whether creepers, endermen, ghasts, and withers should be able to change blocks.
• naturalRegeneration - Toggles natural health regeneration
• randomTickSpeed - How often a random block tick occurs (such as plant growth, leaf decay, etc.) per chunk section per game tick. 0 will disable random ticks, higher numbers will increase random ticks.
• reducedDebugInfo - Whether the debug screen shows all or reduced information.
• sendCommandFeedback - Whether the feedback from commands executed by a player should show up in chat. Also affects the default behavior of whether command blocks store their output text.
• showDeathMessages - Whether a message appears in chat when a player dies.

Source: Minecraft Wiki

In Minecraft, you can type /gamerule Tab and keep pressing Tab to iterate through all (if no hidden ones) available game rules. When the rule you want appears, just press Space and input either true or false.

I believe the rule name itself is already quite self-explanatory, if not you can refer to the list above or the Minecraft Wiki or try them yourself.