Preface
I think I've been pretty harsh in voting and slaughtering. I've seen other people with 200-1000 accepted themes from slaughtering, while I had only about 40. My reasoning is a mix of: the theme should not imply the gameplay too heavily, the theme should not be a repeat of a previous event (though I don't have the knowledge to have managed that), and the theme should not be related to the Hitchhiker's Guide to the Galaxy.
But now it's personal. I've spent my voting on themes that would be fun (in my very personal, subjective opinion) and that I feel instant inspiration from (that can be managed in 48/72 hours). Still seems pretty harsh.
Round 1
Shoutout to inconvenient super powers. It sounds like a theme so fun I'd build something around it outside of a jam. I actually like a lot of the ideas, but feel they're either too limiting/hard for a jam or too specific of a mechanic for a game. Vagueness seems to work best.
[-] One bullet
[-]One minute
[-] Dying planet
[0] Ancient world
[0] Two points of view
[-] Fragile
[+] It's spreading
[-] Inconvenient super powers
[+] Start with nothing
[-] Running out of space
[-] Nothing is explained
[0] If you don't see it, it doesn't exist
[-] Color as a gameplay feature
[+] One enemy only
[0] Build a dungeon
[-] Control two things at once
Round 2
I'm a sucker for rule-based limitations, but I don't know how well a lot of other people would handle them in a jam time limit. So between the round 3 rule-based theme and this round's one, I'd rather 3 rules. It's also far more open to interpretation.
[0] Light is key
[+] Evolve
[-] You start with everything and end with nothing
[-] Four elements
[-] Decay
[+] Use the enemies to win
[0] Duplication
[+] Expanding environment
[-] Safe in the dark
[-] Tiny machines
[+] 3 Rules
[-] You can't control the player
[-] Alchemy & Magic
[-] Four-colour palette
[-] What you create you must destroy
[-] One of you is a traitor!
Round 3
Maybe if rules changing wasn't tied to failure...? Maybe if it was just a statement that rules change? Either way, shelter seemed vague enough and you are the final boss seemed fun enough.
[-] It's not a bug, it's a feature
[-] You can't save them all
[+] You are the final boss
[-] Death is useful
[-] Find it, protect it
[-] Shadows
[-] Light is dangerous
[0] The game rules change after each failure
[-] Floating islands
[0] the more you use an action the worse it will perform
[-] You control the environment, not player
[-] Craft your own magic
[-] I have been here before
[-] You are not the main character
[+] Shelter
[0] Night is coming