Gauche is excellent for system programming but obscured by Guile.
Gauche is indeed very solid as a glue language for daily plumbing tasks.
Another great thing about Gauche is that it works very well across platforms. When I was first getting into programming I was running 32bit OpenBSD, and it was the only implementation conforming to R6RS or R7RS that I was able to run. It also has great documentation on their implementation of the specification and what this means for programmers (for example strings are immutable). It also tends to encourage standard compliant Scheme, primarily extending the standard for historical limitations of the standard and SRFI, and depreciating these deviations over time.