I know some are cold-blooded, so if some are, then there has to be an opposite.
Do you mean other than bankers and lawyers ?
Depends on how you define "warm-blooded", or even how you define "blood".
If we limit it to organisms that are able to generate and contain heat within their bodies then the hummingbird hawk moth probably qualifies. There's even a fish, the opah, that's now classified as "warm-blooded".
And some species of Tuna.
Insects don't have "blood" as we define it.
All insects are cold blooded. Or rather unheated ;) A fly sitting on a hot rock may have hotter blood than us.
Internal temperature regulation was invented back in dinosaur days when the big problem was to cool down those huge bodies. They tried a lot of ways, like this fellow with 'cooling fins' on his back:
The Insect family branched off long before the dinosaurs appeared. They never grew big enough for metabolic heat to be a problem, so insects are all cold-blooded.
