There was an axiom in 3rd edtion 40K: Never fight the Catachans in the Jungle. They got all sorts of wicked benefits, and their low armor was negated by having cover saves everywhere.
During my first summer at college, we used to play in Joe's garage. Joe's army choices at the time were the Angels Sacrosanct, a Blood Angels successor, and some Catachan Jungle Fighters. Once, in Joe's garage, we set up a jungle fight. We used a green board, some tree bases, and created some white paper templates and strips about 3" wide. The templates were clearings, and the strips paths. Everywhere else was forest. Who wanted to fight the Catachans in such terrain?
Enter the Azure Flames, newly swelled from almost a full summer of obsessive-compulsive collecting and painting. I took a 1500 point list that contained 11 flamers and 2 heavy flamers, all infantry. I marched across the board, burning as I went. Catachans don't get cover saves from flamers. Embarrassing Jungle Fighters in the Jungle is impressive.
Joe got his revenge. In a normal later game Joe took a Leman Russ battle tank that sat hull down behind a chest high wall, and shrugged off every weapon fired at it. Worse, he had some decent close combat ability, which killed at least one squad. However there was a silver lining. One tactical squad was whittled down to one bolter marine who stood toe-to-toe with a commander with a power weapon and a commisar with power fist, and a command squad. This lone marine stood for SIX ROUNDS OF COMBAT, killed a few guardsmen and fought so fiercely that the commander would have fled, had the commisar not shot him in the head! This marine was the first of my models that earned a name. Brother Jonathan of the 2nd squad 4th company. I still field him on a regular basis.