What are some different interactions where photons are released?

PiChiNietzsch

Pretty simple; what are some different ways that photons are released?
Specifically, I'm looking for a short list of different particles that will release a photon in any given interaction.

Tried googling, but its amazing how difficult it is to find an answer to such a simple question -- basically, someone is telling me that photons are released exclusively by electrons, but I'm 99% sure that isn't true and just want an external source other than my own mouth to be able to correct them (the first thing that pops into my head is a proton and antiproton annihilating each other into pure energy - two high frequency photons).

Who knows, I might be wrong though, and could just be entirely deluded with what I thought I knew.. But I think since 'how an electron produces a photon' is one of the first examples a textbook/teacher gives when teaching electromagnetism and the photoelectric effect, so it'd be easy to make the mistake of thinking its the only way a photon is released especially if no more examples are given.

Also, I've got another question if anyone can give me a quick solid answer:
When two protons (just two protons, aka two positive +1 hydrogen ions) get in close proximity to each other and repel each other since they both have a positive charge, is this repulsion mediated by a photon or just the electromagnetic field of the protons themselves?

mathman

Many nuclear reactions, such as radioactive decay, produce photons.

mfb

All charged particles (=all elementary particles except neutrinos, gluons, the Higgs boson, the Z boson and the photon), in electromagnetic interactions.
While this might be possible, it has to be extremely unlikely. The usual process is the emission of several pions.
Most everyday effects involving light are related to electrons. Nuclear processes are very high-energetic, and those photons are usually gamma rays (with a few exceptions).

You can describe it with the exchange of virtual photons, which is just another way to say "it is the field".