I've been wanting to do this for some time but always get caught up in the excitement of the upcoming season. That said, quite a few years ago I noticed that not everyone was wearing the 'tried and true' Riddell (the GOAT still does):

So, here's a "Viewer's Guide" so that maybe you can identify what each player is wearing (if you're so inclined). I did my best to use arrows (red, mostly) to identify unique characteristics of each helmet shell.

Disclaimer: There is an awful lot of technology involved with today's football helmets. I did not delve into that particular area. I just tried to provide some visual cues so as to identify different manufacturers and models.

Riddell
Riddell's top-of-the-line helmet is the Speedflex. It is easily identified by the unique "U" shaped cutout on the crown of the helmet:

There's also a ridge that runs horizontally across the rear of the shell:

The vent holes also create a unique pattern, as seen from the side. There's also a slight raised portion that forms a kind of "mohawk" that runs all the way to the horizontal ridge:

The remaining Riddell helmets (Speed Icon, Speed Classic and Speed Revolution) appear to use the same shell, the differences are internal. These helmets also have the raised 'mohawk' feature but it only goes are far as the top of the helmet before it disappears (blue arrow). The ear hole is diamond shaped with the area between the hole and face mask protruding slightly. The rear horizontal ridge is also present but is lower and closer to the neck pad. From the back, there are two vent holes, at the top of the helmet, that angle inwards, slightly.

Schutt
Schutt seems to have two "top-of-the-line" helmets in the Z10 and F7. Again, internals are different on each model and the Z10 seems to use the same shell as the rest of the Vengeance line. The F7, on the other hand, is very different, visually.

F7
The F7 has a very unique 'box' that is referred to as "Tektonic plates". These plates allow movement in three dimensions. It also has slot shaped vents at the shell's rear:

Vengeance
The Vengeance Z10, Vengeance Pro, Vengeance VTDII and Vengeance DCT all use the same shell with the Z10 having an additional vertical "chevron" shaped hole just behind the ear hole (the remaining models do not have this). There's also a recessed 'channel' that runs from ear hole to ear hole along the rear of the shell. The 'mohawk' style ridge, along the top, is wider (than Riddell's) and has a saw-tooth appearance on the edges. The vents holes are incorporated into the periphery of this raised area.

Z10:

Pro, VTDII & DCT:

AiR XP
The shape of this shell is simpler than the Vengeance line. Instead of the recessed channel, there's a simple ridge that runs from ear hole to ear hole. Venting is provided by slight larger round holes, arranged in a circular pattern, at the top of the shell.

Vicis
The Zero 1 helmet has rather distinctive vent slots at the top of the helmet, triangular vent holes just above the face mask and a larger than normal 'slot' type ear hole. The rear vents angle outwardly. According to their web site, they will be outfitting Notre Dame, exclusively, this year.

Xenith
The Epic helmet has a rather smooth shell with vent slots along the top. They angle outward from just above the face mask and then meet and cross at the back of the helmet (forming a subtle "X"). Xenith seems to have very different face mask configurations (as compared to the other manufacturers).

If any of you are more familiar with these products, please provide feedback. I know there are a lot of folks on this site that are much more intimate with football equipment than I. I just hope I can make your football viewing a little more enjoyable. Thanks for reading. Go Blue.