First I'll do some most known then later I'll do the least known.
1). Beauty and The Beach
(James with fake boobs in a bikini making fun of misty's, here in the U.S. it cut out some things to make it "appropriate").
2). The Ice Cave
(Jynx was included in the episode, but since her face looked a bit black they banned it and changed her face purple).
3). Terror Tower
(Banned well only for 3 yrs. because of the attacks of 9/11 then it was released).
4). The Legend of Dratini
(Showed people with guns pointing at ash. That was the episode that ash catches all Taurus in the Safari Zone with the "Green Pokeball").
5). Most known episode: Electric Soldier Porygon
(You might know this episode because it supposedly gave 685 kids seizures, because of strobe lights.
Fun Fact: One of pikachu's moves known as 'Pokemon Shock' was banned do to lots of lights flashing which also caused several seizures)!