I have always been partial to .uha, the files produced by Uwe Herklotz' UHARC archive utility. I mostly ran into them on pirated game rips downloaded from DALne

I have always been partial to .uha, the files produced by Uwe Herklotz' UHARC archive utility. I mostly ran into them on pirated game rips downloaded from DALnet IRC in the 90s and early aughts. It's extremely slow, however. If I was going to be packing lots of data I'd probably use mopaq (.mpq) which has support for LZMA and Huffman coding.