I used to amuse myself by returning to the swamp during disc three and slaughtering many thousands of Zoloms.
Well, not that many, but it's still entertaining to make short work of the serpent that everyone's wetting themselves over during disc one. Also, getting Beta, as has been mentioned, makes the Enemy Skill materia all the more powerful.
It's easy to avoid the Zolom even with no Chocobo... you just have to save your game when you're halfway across the swamp, before the Zolom gets to you. Then, if you're killed, just continue from where you saved. The Zolom will have to re-start from way back on the other side of the swamp.