It occurs to me, building my Tyranids Start Collecting set, that there isn't really much point in keeping the spare parts. Tyranids have a really comprehensive range. If a creature can have a weapon then that weapon is going to be right there on the kit.
A bunch of spare parts are going to my friend Matt who is using them to manufacture Chaos things for his Lost And The Damned. Some of the smaller bits, however, I'm going to hold on to so I can make some Ultramarines Tyrannic War Veterans. I don't want an Ultramarines army, as interesting as I find them I just know I'd end up bored out of my mind painting that much blue. A single unit, though, that's interesting to convert and paint.
I also admit there's a certain pleasure to having a small Ultramarines force made entirely out of a non-Codex unit. Also, as Veterans its another excuse to work on painting white.