Weapon speed. While these rules add an element of realism to the game, you have to go as far as the introduction to see Gary Gygax write that realism wasn't a design goal. Wise man. In actual play, I've found that artificially forced realism by way of rules like weapon speed does more to detract from a D&D game than add to it.
Grappling. In fairness, I dislike this about every edition of D&D. As with weapon speed, I've never found the grappling rules to add to the D&D experience. Most everybody that I know (again, in every edition of D&D) has used a basic series of "To Hit" checks versus armor class to resolve grappling -- and games have been better for it.
XP for treasure. I always found it odd that many of the AD&D designers complained endlessly about Monty Haul games. They obviously didn't get it. The rules specifically rewarded players for accumulating treasure. If you don't want people to make treasure the focus of play, it probably shouldn't be the foundation of the game's primary reward mechanism. I mean, duh. At any rate, treasure should be its own reward. Life experience should be awarded for deeds.