1. Nob Bikerz were a ton of fun to convert, especially since the new Biker Boyz kit had just been released.

2. Flash Gitz were similarly damn fun to make. I built mine before the new kit came out, using the then-new Nobz box, the Nobz from Black Reach, and about a ton of other gunz and gubbinz. I've been doing similar with Lootaz recently, although using standard Boyz bodies

3. Kommandoz! One of my first serious conversions, mine were mostly made of Ork Boyz and Catachans, with other bitz sprinkled throughout. Lots of personality and fun went into them. Of course, they just sit in their case these days, but they at least look cool.

4. Can I say the entire Dark Eldar line? Fantastic models, great posing, nicely modular... if I'm forced to pick, I'll say the Scourge. Cool-*** models, nice options, great unit. The Raider might take second place... the dudes you can model just hanging off the side are awesome.

5. SM Devastator Box. This thing has fueled many a conversion. So many useful bitz! Related, the Catachan Heavy Weapons Squad box. Lots of guns, sure, but also some great knives, grenades, and scenery bitz. Good stuff.