1. A quick save button, without having to open the menu.
2. Always be able to wield the weapons used by enemies and that they drop the corresponding ammunition, not only sometimes.
3. From here this becomes more crazy/difficult. Bullet time to dodge projectiles and be able to destroy enemy projectiles with your own projectiles, with cooldown.
4. Radar in a corner of the screen, to detect most of the enemies and hazards.
5. Invisibility as a single use item but you can activate it by pressing a button, not by picking it up.
6. Time reversal field: a field is formed around you where time is reversed, reversing the trajectory of incoming projectiles and heading towards the enemies that fired them, possibly injuring them, with a cooldown.