Quote Originally Posted by Godskook View Post
According to the wiki:

Tiger Udyr's persistent effect procs lifesteal.

Kayle's E procs spellvamp

Cho's E procs spellvamp(arguably not an on-hit at all, but still)

Jax's ult procs spellvamp

Darius' passive has mixed listings about its ability to proc spellvamp, but I can't test it as I don't own him yet.
Kayle E and Cho E are both distinctly unlike traditional on-hit effects as both abilities significantly change the way in which their champion's basic attack functions. Jax's ult is also consistent with how other on-next-attack abilities (Jax W, Rengar Q, Darius W, etc) interact with lifesteal/spellvamp, the only difference being that the skill itself is a passive, so I would hesitate to describe it as an on-hit in the same way that Teemo E, Twitch passive, Irelia W, or Yi E are on-hits.

my testing suggest that the persistent effect on udyr's q doesn't interact with lifesteal.