Some of the first gladiators had been prisoners-of-war, and so some of the earliest types of gladiators, Gauls, Samnites, and Thraeces (Thracians) used their native weapons and armor.
Different gladiators specialized in different weapons, and it was usual to pair off combatants with widely different, but more or less equivalent, equipment.
As a rule gladiators only fought others from within the same school
Here’s a sampling, though you can get the full list from the Wikipedia article linked below:
- Arbelas used a crescent shaped knife (normally used by shoemakers to cut leather), but in the games used primarily in knife duels.
- Bestiarii were the beast-fighters, of which there were two types – the condemned set up to die, and the volunteers seeking glory. Technically, “gladiator” only refers to those who fought humans, but these were very much part of the games.
- Bustuarius were the “tomb fighters” who fought during funeral games as a replacement for an older custom of putting captives to death at the graves of famous and strong men.
- Cestus wore a battle glove, an antecedent to the modern boxing glove. But much meaner.
- Dimachaerus fought with two swords at once, generally a pair of siccae or gladius.
- Equites (horsemen) and Essedarius (charioteers) sometimes continuing the fight dismounted after an initial clash.
- Hoplomachus were meant to evoke the ancient Greek hoplites, and so were armed with a bronze helmet, manica armored sleeve, throwing spear and sword.
- Murmillo armed as a Roman soldier with rectangular scutum shield, bronze helmet, and gladius.
- Retiarius fought with net, trident, and four-spiked dagger – and without a helmet.
- Sagittarius were mounted archers armed with a reflex bow.
- Scissores used a specialized short sword with two “scissored” blades, possibly to entrap the opponent’s weapon.
- Secutor (“Pursuers”) fought with gladius and a special small-eyeholed helmet, manica and scutum for protection. Paired against the net-wielding retiarius, his heavier armor and shorter range meant he had to close aggressively if he were to win, which explains the name.
Via Wikipedia with the exhaustive list.