There's an old game I grew up with called Castle of the Winds. You could also move using some other keys or the mouse, but for me my favorite way by far was using the numpad with numlock turned off.
I also used to use the numpad while playing Half-Life, as the person who introduced me to that game swore by remapping all the keys to the numpad.
Favorite? Pretty much what everybody else says. Portability. Battery life, all things considered. Controls feel great. Amazing handheld for emulation. I have an electric car, and I love being able to use my Steam Deck whenever I'm waiting for my car to charge.
My least favorite? The touchscreen. It's garbage. I was excited thinking I could play Osu on it. Nowhere close. It's not really even accurate enough for higher-level Plants vs. Zombies. You'd think a device like the Steam Deck would be great to dual-booted or virtualize Android on, but with the crappy touch screen, I can't recommend it. But the worst part is trying to use the on-screen keyboard with it. I use my Steam Deck as a PC replacement at work. I'm a sysadmin, I've been using Linux for two decades, but the touchscreen makes even the most basic terminal commands painful to type with the OSK. So if you plan on using it heavily as a PC, or doing a lot of tinkering with it like I do, do yourself a favor and get a physical keyboard for it. Bluetooth ones are okay, but having a full-blown keyboard, mouse, and monitor with USB-C dock is definitely nice if you're using it for more than just a game console.
Pretty much anything that let's you belt it out and really yell into the mic.
Most songs from Blink-182 are fun to sing.
+1 to Sweet Caroline by Neil Diamond, that's a classic.
I Guess That's Why They Call It The Blues by Elton John
Either Get Ready to Die or Party Hard by Andrew W.K.
Come to My Window by Melissa Etheridge if you can hit the high notes
Gompie's version of Who the X is Alice? If you have an audience that doesn't mind cursing and might have fun singing along.