God Hanuman is the incarnation of Lord Shiva.
He is a great devotee of Lord Rama.
He helped to Rama in the war with Ravan.
Mace (Gada in Hindi) is the weapon of this God.
The other name of Hanumanji is Mahaveer, Pavan Suta, Bajarangbali, Kesharinandan etc.

Here, is the story of God shanidev & Hanumanji.
As per Hindu Epic Ramayana, When Hanuman went to the Lanka in search of Sita mata (Wife of Lord Rama).
After meeting with Sita mata, when Hanumanji was coming back, he met with many God who were in clutch of Rakshash (Evil) King Ravan.
God Shanidev was also there.
Hanumanji helped freeing shanidev and getting out of Lanka.
Because of Hanumanji helped Shanidev they both became friends.
Here, Shanidev Promised to Hanuman that anyone who prayed to him (Hanuman), he would be rescued from the baleful effects of Shanidev.

Other story of Shanidev and Hanumanji:God Surya Dev is the Father of Shanidev.
Surya dev is also the Guru (Teacher) of Hanumanji.
After the completion of course, Surya dev said to Hanuman, “You have become adept in all forms of wisdom and weapons, now go to your mother Anjani” But Hanumanji requested to Surya dev “Give me an opportunity to repay for your tutelage” Suryadev said to Hanuman, “my wayward son shani is the cause of my sorrow only, Go and bring that wayward son of mine back to me”.
Listening to the order of Surya dev, Hanuman went to Shanilok.
When he was going to shanilok many planets tried to stop him but they were unable.
When Shanidev saw hanuman he asked to him, “Who are you? Why are you come here? Do you not fear with die?” Hanumanji replied, “I am Hanuman, The disciple of Lord Surya.
Lord Shani you have all power & virtues, but your greatest drawback is disobeying your father.
It’s not good & it’s the greatest sin.
I have come here to take you to your father.” Hearing all this Shani became angry & said, “You don’t know my power, Powerful god also trembled with my power so better thing for you go back immediately otherwise I will burn you” Hanuman replied, “I have not came here to go back”.
Then Shani Dev crooked gaze on Hanuman but shanidev could not burn him so, Shanidev sat on his head.
They were inside a room.
Immediately Hanuman increased his size because of which shani pressed between hanuman and the ceiling.
When the pain was unbearable, Shani requested to God Hanuman to release him.
When shanidev became free from Hanuman then shanidev Promised to Hanuman, “Anyone who will worship you on Saturday, I will never be terminate them.” After that shanidev & hanumanji went to Suryadev.
Shanidev became happy to see them.