If this is an open forum about rules discussion, then the ones that bug me are:
1. A charge down or defender playing at the ball with their legs or feet shouldn't restart the tackle count or give you a scrum feed if it goes into touch. If you're not good enough to get the kick through the defensive line or before a defender comes to tackle you, you shouldn't get potentially rewarded with 6 more tackles. Obviously you can't have fullbacks intentionally kicking a ball near the sideline into touch to get the scrum feed, so you'd need to word this right.
2. I like the 7 tackle rule for kicks that have gone dead or touch in goal, but I don't think it should apply for knock ons over the line. The intention of the rule was to stop teams intentionally kick it dead to minimise the risk of attacking fullbacks making a break from the kick return, and to promote teams to run on the last instead of kicking it. I don't think the intention was to disadvantage someone trying to reach out and score a try and losing it in the process. A 6 tackle set in that case is enough IMO.
3. I hate players staying down for crusher tackles. I can't remember when a player actually had to leave the field following a crusher tackle. I think we've gone past the point of players using them as legitimate wrestling techniques, and all the crushers that now happen are accidents. If the ref isn't able to call it straight away, then it's play on. The Match Review Committee supposedly watches every match, so they can still cite someone if necessary. I don't mind players staying down for high tackles as if it isn't serious enough for getting charged, then it's play on (and the refs miss some doozies), but it seems every crusher tackle goes on report, no matter how minor or accidental. It's a blight on the game, and it happens pretty much every game.