I have a Rittenhouse 21 which is stunning, but for
my money the Sazerac 18 is a better bet. The thing about bourbon
and rye is it's down to the percentage of various grains in the
mashbill so you can have a rye that tastes much closer to a
bourbon than to other ryes. To me the Rittenhouse tastes more on
the bourbon end of the spectrum and so for something more
unusual I'd go for the Sazerac.
On the bourbon front
if you can get an Evan Williams single barrell, I think this is
a good staging point from Irish / Scotch to bourbon - the heavy
wood / vanilla thing is more understated than other bourbons
I've tried.