My guess would be either Abra(always teleports) or Porygon(9,999 coins at game corner). Of course the ones that require a trade are hard to get as well such as Alakazam and Machamp.Which Pokémon(one or more) did you find difficult to catch?Update:Oh, I hated the Safari Zone. They should have just let me used my Charizard.. Created by Inspector no name. entertainment-music-en - comics-animation-en

I would say Dragonite. Since you have to catch Dratini in the dreaded Safari Zone (by fishing), then level it all the way up to level 55 to get Dragonite. Seriously, by the time you get Dratini to Dragonair, you probably already have a good enough team already. The other two starters are pretty hard too (who is willing to give up their starter? Especially in Gen 1 without breeding).