If we're going down the technology route, the offside rule is the one to go for IMO.
How many replays do we see where play is stopped for an offside only to see the striker level and through on goal.
It would definitely lead to more goals.
Think I've mentioned this before but in my only visit to watch a game of rugby at the millennium last year, when the game was stopped to check with the " 4th official" or whatever, the actual footage was shown on the big screen for all to see and I found it to be an enjoyable part of the entertainment, same with the cricket.
I understand people don't want the game made sterile though.