There are many long cooldown/OP skills that are forbidden in 1v1's:

Champ bubbles, dire need
Burg knives out, touch and go etc.
Reaver dying rage, against the odds
Warden defiant challenge, never surrender
Mini triumphant spirit
Captain last stand
Blackarrow moving target
Lore-master wisdom of the council

There's a couple to name a few

If you're going to 1v1, stick to the rules, otherwise you get ganked and get no respect

Firecaster, Kirves, Rodriques