A little bug exploiting bridge over water, you can drive on the gates. With night settings it creates a very nice colorchanging effect for the true gamers among you.
bug not found by me; i learned this through Robyn mentioning it to SBVille.
it even works freeblocked, so you can place this upwards, downwards whatever you'd like, however the water block can not be facing some directions, if you want the bridge to continue that way, place the macro and then remove the water, and place a new water block
Double lane version without water block: