Since everybody is suggesting fuzz/overdrive/distortion, I have to ask. Does anybody use that realistically outside of metal?
Do you listen to music? I mean really listen.
Uhhh...let me think. Yes. Other genre's of music use fuzz/overdrive/distortion. If you need specific bands or genres, I suggest you search Youtube and listen to the radio.
As far as what you "need", well it depends on what you want to accomplish. I know a lot of people would suggest you don't need any effect to get a good bass tone. Others swear by them. It just depends on your outlook. I think subtle effects are awesome, but I obviously also love insane effects. Effects can be fun and useful depending on what type of music you're into.

