[Ichneumon]

[leaves me wondering what the *first*-most abundant cellular protein might be]

A piece of the larger Ribosome?

I haven't found an answer for animals yet, but apparently the most abundant protein in plants is Rubisco (also often named as "the most abundant protein on Earth"), and for prokaryotes it's elongation factor Tu (EF-Tu).

[donh]

Rubisco (also often named as "the most abundant protein on Earth"),

Because no creature can resist those rubisco crackers with the cream filling.