My group moved away from D&D to break out of old familiar patterns and habbits and we succeeded while we explored the White Wolf's World of Darkness. Returning to D&D everyone is leaping headlong back into their old habbits. Welcome back spike chain, enlarge spell, combat reflexes. Welcome back crafting and the magic item sweat shop. Welcome back halfling dog riding sling weilding druid/rogue. Welcome back fighting over and hording magic items.
How do you get veteran players, playing a system they know extremely well, to do something new?
Now let me give you a real monkey wrench; Our DM only allows the Core rules. (Player's Handbook, Dungeon Master's Guide, Monstrous Manual).
*Offers Monkey the Uber Monkey Wrench +6* It's anti-theft.
Anyway, I know Harpy will probably answer this anyway, but hey, I want to give my own solution too. Throw something different at the rest of the group(But stay in D&D when you throw this different thing at the group).