I was playing the Into the Multiverse maps on Portal 2 recently, and I noticed some things that would be fun to create ...
UNIQUELY COLOURED TURRETS! (wow!)
VERY BIG NOTE: I have had to substitute a lot of pieces in the turrets, as I do not have them and they are not available on Lego’s Pick a Brick, and I think they look fine without the correct pieces (some of the black pieces in the TNT turrets are one example). If you do have parts that are a better fit, feel free to do so.

Supplies

See my other instructable on how to make a portal turret - you will need the same pieces but in different colours for most of them.

Step 1: Defective Turrets

This is the turret design that is different, because it is missing 2 pieces that give regular, non-defective turrets their shape, creating a more skeletal feel to the build.

Step 2: Blue Turrets

The picture I took showing all the parts required was hard to make it so that viewers could see the said pieces because the background was blue, and so were most of the pieces! In the end, I achieved a good-ish result!

Step 3: TNT/Red Turrets

These turrets have been directly pulled from the Portal 2 ‘TNT turrets trilogy’ set of maps. In the series, all regular turrets are replaced by red turrets that detonate after a brief countdown when picked up.

Step 4: Black Turret

This turret may look like the defective turret, but it is not lacking some parts of the outer shell, making it count as a real turret.
NOTE: to make this turret, see step 1 on how to make a defective turret, because this turret only has 2 extra pieces than the defective turret.
So really what you should do is build a defective turret and start with that.

Step 5: Dilapidated/grey/gray Turret

This type of turret is seen in Portal 2 when the junk comes out of a vital apparatus vent instead of a weighted storage cube in Chapter 2 test chamber 6. I have uploaded a picture of it here in-game, too.
You can actually make a turret in-game that looks like this without being in that chamber by finding a turret (if you want to summon it with the developer console, the command is ent_create npc_portal_turret_floor), looking directly at it, and opening the developer console and typing ent_fire !picker skin 1
You should now have this turret in a test! This also works in the perpetual testing initiative, which is how I got my picture. I also used the command notarget , which makes turrets unable to detect you.
NOTE: both of the 1x2 flat tiles don’t have to be grey/gray, as long as one of them is grey/gray then it doesn’t matter what colour they are. The best alternate colours are dark gray/grey and black. Any printing on the bricks is good, too!