Taking smite just for jungle items?

Trundle in the top lane can do it. I suppose a champ who lacks CC and/or wants to rush Devourer can do it as well.

It's something I've been wanted to test, but it's hard to justify taking it in any lane. Top lane needs teleport to be relevant, risky on ADC, and it's hard to justify losing kill potential / safety for wards mid.

I know people did it a lot at the beginning of last season. I havent seen anyone do it since then, however.

At one point ap ezreal mid with smite was a thing just for the ap jungle item. Thats dead already but I still see some people trying it out without success because it doesn't work the way it did before. I can still see being a thing because extra health based on percent can be really strong on a tanky top like shyvana or maybe singed. I'm going to try that out later. singed with the blue smite for chase potential and super tankiness.

Ez mains used to go mid and rush runeglaive.

I do it with and some other Supps, like this I build for wards, which means I get a good version of wich can be upgraded into something decent, it also allows me to do dragon and objetives more quickly.

This used to be a thing. Back when Cinderhulk was first introduced some top laners went Smite + TP top to abuse the dueling power of Skirmisher's Sabre with the hyperscaling tankiness of Cinderhulk. Shyvanna and Hecarim were the most prominent abusers of this strategy, although they weren't the only abusers of this strategy. I remember Huni utilizing this strategy on Lee Sin in the LCS with moderate success.

Runeglaive also had seen some use in the solo lanes, with AP Ezreal and AP Gangplank being the most prominent abusers of it. AP Ezreal in particular I believe was pick/ban at the time for his synergy with Runeglaive. There weren't a whole lot of other champions that used this kind of strategy, although I do remember PowerOfEvil playing it in the LCS, even getting a Pentakill with that build.

That said, the jungle items aren't nearly as strong as they were before, so it definitely wouldn't be worth trying to get those items for the lane. Devourer isn't viable on laners due to the requirement of taking jungle camps, Warrior is too generic to actually be worth using over other alternatives, and both Cinderhulk and Runic Echoes have valid replacements if you want their most important effects while getting more stats and not having to use smite. Cinderhulk can easily be replaced with Sunfire Cape and Runic Echoes can easily be replaced with Luden's Echo, so there really isn't any point in getting the items for the jungle enchantments.

Whats the point now? It used to be but now Cinderhulk is weaker than Sunfire and Echoes is weaker than Ludens.

I would do that in urf. Last year's urf no one takes smite to jungle since it was pointless; pretty much everyone jungles and with 80% cdr smite isn't needed to clear camps. However, I feel that sated helps xin so much in urf I actually need it. Increasing knockup frequency from once every 3 auto to once every 2 auto is huge - with sated aspd and w always active you can pretty much keep your target in the air all the time, and nothing his opponent can do about it since neither tenacity nor quicksliver helps.