Are mitochondrial genes to exclude in scRNA-seq such as ribosomal genes?
According to Ilicic et al. (2016), on upregulation of mtRNA in broken cells:


  There is an extensive literature on the relationship between mtDNA, mitochondrially localized proteins, and cell death [34, 35]. However, upregulation of RNA levels of mtDNA in broken cells suggests losses in cytoplasmic content. In a situation where cell membrane is broken, cytoplasmic RNA will be lost, but RNAs enclosed in the mitochondria will be retained [...]


According to this, I think that mtRNA levels relative to endogenous RNA can be used as a control for low quality (broken) cells, in a similar way to ERCC spike-ins.


Ilicic T, Kim JK, Kolodziejczyk AA, Bagger FO, McCarthy DJ, Marioni JC, Teichmann SA. Classification of low quality cells from single-cell RNA-seq data. Genome biology. 2016 Feb 17;17(1):29.