Just had the exact same thing and I think I figured out the issue (for once)
I got underneath the dash with a flashlight (not easy!) and studied it, and saw that at the point where the clutch pedal attaches to the actuator rod. As you will see, the clutch pedal has a solid metal nub that goes into the round hole of the actuator rod. There is a little plastic bushing that slips over the nub and holds it in the hole. That is a piece of crap part and tends to break after a few years of use.
NOW here is what happens to cause the "wiggle" or play in the pedal, and what happened to mine:
Without the plastic bushing (or if the bushing breaks a little but hold together) it creates play at that connection. If not addressed right away, during the thousands of times you press the clutch pedal, the metal nub actually wears against the hole of the actuator rod, and instead of a circle, you will get something like an oval shape (again from the back and forth metal-to-metal contact over time). This allows the nub to move back and forth a slight bit even though still attached to the rod, and that is what causes the clutch pedal to wiggle or rattle over bumps. Honestly, for two years, my plastic bushing was completely broken, and I have no idea how or why my clutch pedal stayed attached to my actuator rod!
To fix mine, I got a piece of nylon tubing, some washers and a couple c-clips. I slipped a cut down piece of nylon tubing over the clutch pedal nub. This helped make up for the "oval-ness" of the clutch actuator rod hole and make a tighter fit. Now, put the nub through the hole and put one or two washers over the nub. Use the c-clips to hold it all together. Works great and saved me from buying a new actuator rod/slave cylnder unit.
NOTE: If your actuator rod hole is worn and made into an "oval" like mine was, buying a new plastic bushing from Jeep or anywhere else WILL NOT WORK. I tried. This is because the play at the connection actually crushes the new plastic bushing the first or second time you depress the clutch pedal. Once the bushing is cracked or crushed, it won't hold the connection tight enough. That bushing is designed only to go into a perfect circle.
To give proper credit for the fix I used above, I got the idea from this fine gentlemen who figured it out and posted a write-up. I don't think he had the oval problem, but the fix works just as well: