Gengar and Snorlax. Snorlax was a powerhouse, he was strong and had massive HP the only downsize being that he was slow, although that didn't matter really since I always won with him. And I love how gengar looks so evil and happy about it, best character design ever. In terms of combat, you just couldn't beat my Gengar easily, he would go through at least 2 pokemon before going down and even if he got defeated there was some move he had that caused the attacking pokemon to faint as well, I think it was "Destiny Bond"
The original versions were great, and I always used those two as well as other original pokemon no matter what version I was playing in, I stopped playing pokemon when I had to worry about how their randomly assigned personalities would affect my battles and when the newer pokemon began looking like Digimon