You really thought, didn't you?
These are some pictures of vents I found online, I'll compare and contrast them with ratings on a scale of 10:
Vent 1:
Starting off with whatever this is supposed to be used for, I think this one would be good for grilling and whatnot, but would allow bugs in and out very easily.
Air flow: 9/10
Looks: 6/10
Versatility: 8/10
Vent 2:
I vividly remember the hot air coming out of one of these, it was from the dryer.
Air flow: 3/10
Looks: 7/10
Versatility: 4/10
Vent 3:
It looks like it could be a shell of some robot, or a hunting thing.
Air flow: 6/10
Looks: 7/10
Versatility: 5/10
Vent 4:
This is one of the A/C vents, it's got cool multi-directional things to spread air.
Air flow: 7/10
Looks: 8/10
Versatility: 9/10
Vent 5:
I have no idea where I've seen this before, but it looks familiar.
Air flow: 8/10
Looks: 8/10
Versatility: 7/10
Vent 6:
My favorite in looks, I don't know where I would use this vent, but it looks like it would also be used for a dryer.
Air flow: 8/10
Looks: 9/10
Versatility: 8/10
Give me your personal favorite, and I know I must've missed a few, because I just had this idea and I just scrolled until I felt I had enough pictures.
Have a good day! :D