Of course I keep my Feraligatr, after realizing how awsome he is. With Substitute, Dragon Dance, Torrent, the attack-raising berry and Waterfall, I'm surprised not everyone picks Totodile, hehe.
On Silver, way back, when I couldn't read English very well, I wanted to know what the Time Machine was. But then it said something like: "I'm sorry, Feraligatr can't be brought". So I released him. Spent hours searching for him in the tall grass afterwards, hahaha!