Top 10 battlefield rifles was led by the SMLE .303 over the K98icon by virtue of the 10 shot mag and rate of fire and yes the Garandicon was a head of its time in design but not sure if the German designed Gehwer 44(I think that's it) assault rifle ranked pretty well also

I'd reckon the 2 worst guns to fire would've been the Boys Anti-Tank rifle and this little gem from the Germans in WW1 which is basically a over modified K98 Anti Tank rifle that from most reports said that whoever fired it ended with either a badly bruised or broken shoulder,regards