It seems the hot topic of the moment... is about Rock Crawlers.
Thus I've selected for this week one video from a true fan of Rock Crawling, who has been experimenting such vehicles with LEGO Technic elements, for long! Marcelo Raus from his name.
This model uses a couple of PF XL-motors (one in each axis) and an M-motor for steering.
Notice it doesn't use original LEGO tires, but some soft rubber ones for optimal crawling performance. LEGO tires would not pass obstacles like these.
But tires are not the only unofficial parts in this model. If you take a look at other videos from this model, certainly you will find more intrusive or adapted parts...
Somehow it confirms the special requirements imposed by a big and motorized Crawler like this one, and supports the ongoing online discussions about requirements from an hypothetical Row Crawler to be released by TLG, as 2H12 flagship for the LEGO Technic theme.
Along the crawlers, Marcelo has also built many other TrTr vehicles and cars.
You may find more models from him, at his Brickshelf folder and huge amount of short performing videos from his models at his YouTube channel.
In the meantime you can also take a look to this other Off Roader from Marcelo.
Don't get nervous... September 2012, is not that far away!...