Also, if you are in the Water, it is an invaluable tool.
I don't know how Nooby you are when it comes to the Fishing Rods, or PvP in general, but:
When Teaming with someone and chasing someone in Water, push each other forwards with fishing rods. If you have even half-decent armor, it will not deal you any damage, but will get you closer to your target.
If you are being chased by someone in Water, push them away from you with the fishing rod! Even better if they don't have any armor, because they could take damage.
Being chased on Land? Hit your opponent away from you by quickly spinning in a 180 twist, hit them once or twice, then turn back, and keep running! A decent way to get some time to regenerate your health.
Likewise with the Water, if you and a teammate are chasing someone on Land, you can hit your teammate forwards with the fishing rod to give them a slight boost. Make sure you don't hit the person you're chasing.
In DeathMatch with a person with: A) Better gear than you. B) More hearts than you. You can use the Fishing Rod to circle Cornucopia and hit them back, giving you time to regenerate hearts.