What got me interested in Robocode was my memory of an article I had read in Byte magazine when I was a mere lad of 13 or so about a game called RobotWar on the Apple II. I never played the game, but the concept intrigued me. There's a screenshot here (http://www.robotbattle.com/history.php) - obviously the guy who wrote Robot Battle was inspired to go a little bit further. I just found the manual for it online (http://files.the-underdogs.org/games/r/robotwar/files/robotwar.pdf).
Regarding Development Tools, I flip between Eclipse and vim as my mood takes me. I'm sure vim isn't for everyone, but I use vi in my day job (UNIX admin - HACMP clusters anyone?) so it makes switching easier. Actually, after another 12 months of using it, I find that Eclipse is so damned good for Java development that I rarely use anything else.