Protecting with symbolism.
by Satish Krishnamurthy
Lord Murugan’s weapon, the vel (spade) adorns the entry passage to his temple at Chedda Nagar, in Chembur, Mumbai.
A quick excerpt from Wikipedia says this about his weapons.
Kartikeya symbols are based on the weapons – Vel, the Divine Spear or Lance that He carries and His mount the peacock. He is sometimes depicted with many weapons including: a sword, a javelin, a mace, a discus and a bow although more usually he is depicted wielding a sakti or spear. This symbolizes His purification of human ills.
His javelin is used to symbolize His far-reaching protection, His discus symbolizes His knowledge of the truth, His mace represents His strength and His bow shows His ability to defeat all ills. His peacock mount symbolizes his destruction of the ego.
There’s also some interesting points about the controversy of Murugan being an Aryan or a Dravidian deity with respect to different Northern and Southern myths, if you’re keen to read it.