Hi @rustx and thanks for posting on the forums! I am a big fan of gaming in Japanese as well and have often been quite vocal that we should have more difficult kanji forms of common words.
Unfortuantely, the problem that we have come across in the past is that because most of these words are very common, for the average student, it can be a little bit daunting when seeing an unfamiliar kanji on a word that they thought they already mastered. I know I certainly felt this way myself the first few times I saw something I didn’t know, only to realize that it was something like それ .
At the moment, we don’t have the option to turn kanji on or off completely, but we are planning in the very near future to have vocab finding features on the site where you would be able to quickly search any sentence on the whole site that has a specific word, and then save the ones that use kanji. We will definitely try to at least include some with the rare kanji!
For now, here is a small list of the words I encounter really really often in games or novels that frequently use their less common kanji structures. Maybe some of our other users can contribute any I missed!
其れ(それ) quite rare (very common in specific games/books).
此れ(これ) quite rare (very common in specific games/books).
筈(はず) not common, but not rare.
一寸(ちょっと) not common, but not rare.
丁度(ちょうど) not common, but not rare.
殆ど(ほとんだ) not common, but not rare.
迄(まで) not common, but not rare.
位(くらい) not common, but not rare.
貰う(もらう) quite rare.
呉れる(くれる) quite rare.
沢山(たくさん) very common.
様(よう) pretty common.
程(ほど) pretty common.
頃(ころ) pretty common.
儘(まま) or 侭(まま) second one is rarer, first one is still pretty rare.
気味(ぎみ) pretty common.
流石(さすが) pretty common.
又(また) pretty common.
You probably already know most of these ones, but this is about all of the ones I can think of off the top of my head that are 100% worth knowing the kanji forms.