Which suction cup toys really work?

I recently discovered the joys of suction cup toys. Unfortunately, some of the toys that are sold with suction cups don't really work. The suction cups are too small or too badly designed to actually hold against a wall once they are in use. I have Bree's Colossal Cock and although the dildo itself is rather challenging (much bigger than I thought it would be when I ordered it), the suction cup works great. More recently, I bought the Wall Banger Double Penetrator and the suction cup didn't work AT ALL. It would hold the toy against the wall, but the minute you tried to use it, even if you were extremely gentle, it would just pop off. I tried it wet and dry on a number of different surfaces, it didn't stick anywhere.

So... who else has experience with suction cup toys and which ones REALLY SUCK? In either since of the phrase.