Grand Olympiad

In the competition are you allowed to use pet summons?

I think the rule is that you can only use a summons that comes from one of your skills, not from your inventory. So, no pet summons, but Dark Panthers and such are allowed.

Before the competition begins, HP, MP, and CP are all recovered and the pre-existing buffs and debuffs will be removed. Any summoned pets will be returned, but the servitors/cubics will accompany the player to the coliseum. The servitor’s buffs will also dissolve before the start of the competition.

. . .

4) In the Olympiad competitions, no items other than soulshots, spiritshots, Echo Crystals, energy stones, and firecrackers are allowed.

Note: My humble characters did not compete, so be aware I have no actual experience there.

Pet summons - no
Servitors - yes (otherwise it would be pointless for summoners to compete :P)