I have several wood paddles, made by an awesome friend (and sometimes 2), that are formidable and VERY effective. They are heavy, thick oak, and a swat covers both cheeks. A few smacks with either is quite intense. I love them for their beauty and creativity and because friends made them for me, but there is lots of pure pain in those.
I also have 2 thinner lexan paddles (decorated beautifully by another dear friend). Those are much less intense and I can take many more swats with them. The sting is, of course, greater than with the wooden paddles. That pain does not linger for days. One of the lexan paddles is roughly shaped like a ping-pong paddle. It has my face on one side and my bottom on the other. Genius.
I think any paddle (wood or lexan, or even leather provided it is intense enough) that can be administered OTK would be my favorite kind of paddle. I greatly prefer the closeness of that position and the natural humility it induces.