I'm sorry if there's already been a thread like this, but I searched the forums and I wasn't able to find anything similar.
VIDEO:
http://www.youtube.com/watch?v=Z30b3-6qdG8
I was just fooling around with Lucas today when I eventually found out that you could sort of L-Cancel aerial PK Fires then connect with something else (A smash, a tilt, an aerial, a grab, a roll, or anything similar).
To do this, simply jump then quickly do a PK Fire. If done correctly, there should be a little time to do stuff in the air right after finishing the lag time of the PK fire. Right before touching the ground, do an air dodge. This lets you touch the ground before the air dodge ends canceling the PK Fire's Lag. From here, you could connect with anything. By the way, this also works with Zap-jumped/Double-jumped PK Fires. Heck, you could even do it with the PSI Magnet.
"Wait a minute, what's the point of using this in an actual match?"
Well, I've tested things out and I find out the doing a fast, wavebounced PK Fire is a faster way of traveling compared to simply running to your opponent. In other words, this could be useful if your opponent's far away and you wanna approach him with a USmash, a grab or an aerial. If he's really far away, you could probably use a magnet pull to approach them.
MAJOR EDIT: Tyr was right. You don't need to pull out your shield. Just press R in the air really fast right before landing, then you could connect with ANYTHING right when you land. I guess I should change the name of the thread.