I have been playing around with compression tools for quite a while, and FreeArc is one of the best of the bunch. It has the best compression / runtime ratio of any compression tool I know. Here are two parameter sets I especially like:

Fast compression

uses 4 cores to the max on a 4GB RAM machine, ~10MB per second. Compression ratio is usually above 7z max, while beeing much faster. Decompression is very fast.

-s; -ma- -m=rep:1024mb+mm+delta+dispack+4x4:lzma:50mb

Maximum compression

Requires 2 pass on a 4GB RAM machine, ~1MB per second. Usually compresses better than freearc’s default max compression. Decompression is fast too, and requires only one pass.

-s; -ma- -m=rep:2048mb+mm+delta+dispack+lzma:ultra:170mb