Trundle: A lot of people seem to just look at his ult and think he is only good at shredding tanks he is a good 1v1 duelist, split pusher and few can beat him in raw ability to take down towers. If you get bored of going top with him hit up the jungle he does very well currently the sustain is real with that passive and W. If you ever get annoyed with certain champs getting tweaked every other patched Trundle is one of the most stable champs in the game and he does not really need anything changed either. One of his core weakness is being kited, so if that does not float your boat don't go for Trundle. Last tip though NEVER EVER PICK HIM INTO SWAIN OR LISSANDRA JUST DON'T.
Tryndamere: Personally i think Trynd is one of the few truly viable Melee ADC in the game right now, though he does see some bans every now and then His ult is a great safety net for those times when you overextend or just get picked out, and his spin does cover ground well as well as jump some of those pesky walls. Other than that though enjoy those manaless abilities and spam away.
Jax & Darius: I know you said you don't won't those "Instabanned" champs, but man I just never really ever see these guys banned anymore. They are both pretty solid and do well in many comps. If the meta does another 180 and push bruisers back into the spotlight then yea you might see them move back into the common ban cycle, but for the most part if you really enjoy them have at it and crush that top lane with them.