[name_u]Rigby[/name_u] is cute!
Here are my thoughts on your list:
[name_u]Austin[/name_u]-I wouldn’t call this unique. This is unique for a girl. But it’s fairly common in boys, which will just make a little girl’s life difficult if you ask me.
[name_u]Evyn[/name_u]-Same as above.
[name_u]Ripley[/name_u]-This is way too close to [name_u]Rigby[/name_u], & also way too ‘[name_u]Ripley[/name_u]’s Believe it or Not’.
[name_f]Tenley[/name_f]-This is not my style. It seems a bit made up & similar to the very popular trendy [name_f]Kinley[/name_f].
[name_u]Harley[/name_u]-This is 225 on the SSA popularity list. Which isn’t unheard of, but not too over done. It’s not my personal style, but it seems to fit your criteria & is cute w/[name_u]Rigby[/name_u].
[name_m]Knox[/name_m]-I don’t know. I like this for a boy, & it’s very masculine in my opinion.
[name_u]Marley[/name_u]-This is about the same popularity as. [name_u]Harley[/name_u]. I personally find it sweeter.
[name_u]Remy[/name_u]-This is a bit close to [name_u]Rigby[/name_u], but a nice choice otherwise. Again, not super unique (537 on the charts, yet [name_u]Remi[/name_u] is 177. [name_m]Add[/name_m] those together, you get a lot of [name_u]Remy[/name_u]/Remis), but cute enough.
[name_f]Hope[/name_f] this helps.