Well I have some ideas for a shield, but most of them are about the mechanics. Also when I would think of a new shield it would be more a utility tool than weapon. My ideas (not all apply for the same shield and they can be combined with other ideas):

- Let the shield be a substitute for a +1 carrot by letting it block one hit and blink the player after while destroying the shield. By this I mean you can instead of have 2 +1 carrots in a level, 1 +1 carrot and 1 1-hit shield to make gameplay more exciting.
- Let the shield time go down quicker when you shoot, so the player has to balance between the offensive advantage and deffensive advantage of the shield.
- Let the shield give a one shot force pulse that clears all bullets around the player.
- As for weapons: A weapon that shoot like pepper spray (with an angle), mid range that explodes with a explosion smaller than tnt but maybe a bit bigger than rf. Also it has a medium-high firerate.

And now a more complete idea: A shield that is made up of oil which looks a bit like a black oil bubble around the player. The player shoots oil bubble bullets with a medium-high firerate of short-medium distance that spread a bit and have tnt size (maybe a fire rate like the toaster or a bit slower). The oil stays for a little time and then fades away making this a more deffensive weapon. Last, the oil does either 2 damage or the oil does 1 damage an can be put on fire to create a small explosion which does 2 damage in a larger area and instantanious. The last one might be a bit too gimmick.