I am currently using this Saitek P2900, only 13 programmable buttons. 2005

Oh god, you must have bought this one because it was all you could get locally or something. I love saitek as much as the next guy, but they sucked when they tried to make a wireless gamepad. The reviews for it sucked, customers hated it. The wired version of this controller was perfection. The crappy wireless technology in it sucked.
I bought the logitech rumblepad 2. Which didn't lose out with the wireless receiver, had twice the battery life, and the win for me was that it wasn't as physically monstrous as the saitek (i have small hands). Still own it, it's just a generic ps2 for pc controller. But, i like others prefer the six face buttons.

The best six button facing gamepad i've ever used was the gravis xterminator gamepad. It had an 8 way pov hat, throttle slider, two analog left and right triggers, two digital triggers tucked under the controller, bla bla bla, plugged into a gameport with an adapter to usb. It was also a very ergonomic gamepad, and those two digital triggers underneath the gamepad were perfectly positioned for your middle fingers to push.

That veho looks like awkward crap. That chinese 25+ button one looks like sex in two hands (i'm buying it). And i must drop the hint bomb for revitalizing an xbox 360 controller as a pc gamepad.
XBCD right here, it lets you do anything and everything to your 360 controller except mapping keys (it's a different driver and also lets you change functionality of the controller like turning an analog trigger into the primary joystick x axis or whatever other things).
Great topic, i know some great suggestions to shop for now
