[C4K3]

I learned about this when I encountered a server with an aggressive fail2ban that wouldn't let me log in because I had too many ssh keys. It apparently counted every wrong key as an auth attempt, so it blocked me before my ssh client tried the right key. Since then I've used IdentitiesOnly=yes

[kenniskrag]

Just add the good key to the ssh config file on the client:

IdentityFile ~/.ssh/some.key