Originally Posted by Darth Cylon
It was after he became Rodimus PRIME that he wielded the lightsaber and shield in season 3.
Hot Rod used the yellow saber and shield very briefly while "training" against an auto-combatant aboard the escape shuttle from Autobot City in TFTM '86.
These stick out in my mind because, ya know, lightsabers. Plus his G1 tech specs ranked him as an "Autobot Cavalier", so being a robot knight with a sword and shield made sense.
On an interesting note, TFTM '86 director Nelson Shin helped animate the lightsaber effects in STAR WARS Episode IV: A New Hope so the appearance of Megatron's purple saber and Hot Rod's yellow sword are an obvious nod to his work.
Any 3P accessory maker reading this please note: You'll have my money if you arm The Cavalier accordingly.