Protect Prayer Guide
I've seen lots of people recently asking what prayers to use for different bosses, so I thought I'd list out as many as I could here.

Note: There may be some missing due to not experiencing them on the server myself and not wanting to give inaccurate information. Let me know what I've missed in the comments and I can add them in.

God Wars Dungeon

Armadyl - Range
Bandos - Melee
Saradomin - Magic
Zamarak - Melee

Dagganoth Kings

Rex - Range Full guide:
Supreme Range
Prime - Magic

Fight Caves/JAD

Waves 1-6 - Melee (I was fine with melee for all these waves, but be aware there are range monsters - Tok-Xil (90) (waves 1, 2 & 5), & magic monsters - Ket-Zek (4 & 5) present.
JAD - All 3 prayer types:  Standing on his hind legs & shooting fire bolt - Magic
                                            Rearing on hind legs and stomping on ground - Range
                                            Reaching forward and biting - Melee

Other Bosses

Kalphite Queen (both versions) - Range
Giant Mole - Melee (although as the easiest boss, it is often not needed)
King Black Dragon - Melee
Chaos Elemental - Magic

Full Barrows guide here:

What to pray for each fight:

Guide Written By Froggy!