I do think I did manage to LetterBomb my Wii, back in the day, but I never liked that console because MoTiOn CoNtRoLs - ugh.
Nah, my favourite would have to be 3DS, with Luma3DS - so much incredibly useful stuff was developed for that wonderful handheld, such as custom themes, NTR plugins, emulators, local save backups, game dumping, LayeredFS mods, FBI for installing CIAs, free Pokémon Bank/editor, and much more I didn't really experiment with. Plus it worked on all console models, and the handheld was inherently portable, so I could take my modded games and installed CIAs wherever I went.
My second is the Switch scene - while CFW is unfortunately largely restricted to launch-model units (good luck purchasing and installing a modchip, if you've never soldered anything in your life and don't have the spare cash for replacement consoles or chips if you screw up...), and the console isn't quite as portable as the 3DS, there's still plenty of stuff on offer.
LayeredFS mods, EdiZon/Breeze cheats, save backups, Tinfoil for installing NSPs and the Eevee Save File Project thingy.