I love his passive during all times of the game. CSing is made easy, you can stack up fast after making a last hit and he snowballs in teamfights when someone dies. A lot of the time, fighting is done near neutrals / minions anyways, just throw a Q and there you go.

Kat's passive is exciting. If you want to maximize her, you have to know how to use her passive correctly which requires fast thinking because she is melee and you generally have to reuse Shunpo to do something again. The passive makes you push more buttons. It makes you move quickly between places. It's fun.

Varus' passive makes your right click a little better. Not exciting, situational, no utility involved.