If you are using Mozc / Google's Japanese IME and ever wondered how to type in a specific symbol or radical, I highly recommend taking a peek at the data sources. Thanks to Mozc being open-source, you can find the respective source file on Github. The second column contains the symbol and the third one the keywords that can be used.

For example if you wanted a symbol for the sun (☀) or a chess piece like the white knight (♘), you can see that the ☀ is a candidate for てんき, はれ and たいよう, and the ♘ can be referred to as ちぇす and ないと.

This is especially useful if you want to know how to type in kanji radicals. While the Wikipedia has a list of Japanese kanji radicals, you might have noticed that some of them won't show up when typing in the reading in the IME. This is especially true for the variants, but already the second radical 丨 can't be found by using ぼう. When looking it up in the source though, you see that it can be referred to as ぶしゅ, いちぼう, たて, たてぼう and こん.