One of my friends played as Chaos back in the day, and he would do all these
"conversions" that involved glueing toothpicks to the guns and sometimes the marines themselves. Like, they'd have really, really long bayonets or they'd have armor covered in really long spikes, so they could jump on you and impale you. Then there was this other guy who played as some bullshit combination of Dark Angels and Imperial Gaurd that he called the "Sentinel Element". Essentially it was so he could use Dark Angels with Imperial Guard tanks.
Oh, and then there was my friend who I played with most of the time. He played as Plauge Marines, and holy shit was he impossible to beat. Like, you'd fight off this whole squad of fucking Plauge Marines and lose half your guys in the process then- OOP, AWWW HE'S GOT LIKE 12 MORE AROUND THE CORNER OOPS.
I played as the most lazy, uninspired DIY chapter of Space Marines of all time. They were the product of my wanting to be Black Templars but being too lazy and apathetic to collect enough decals and also preffering red over white, and thus the "Imperial Champions" were born. Stunningly uncreative name and all. I wanted them to be like specialists in urban combat, but that really never came across. My scouts were fucking badass, though. They cut through a sqaud of Khorne Berserkers without even breaking a fucking sweat, man. I have no idea why, I just always kicked ass with them. One of those freak things, I guess.