If you could suddenly be an expert at any one thing...

[wodaro]

Being an expert with computers would be nice, because every time I try to learn about how they work I get overwhelmed @.@

Another fun one is to be an expert at fishkeeping!! I'm pretty good at taking care of the simple tank I do have, but if I was an expert then I would know how to care for so many unique and exotic varieties of fish! Also maybe I would be able to keep my aquatic plants from dying... Though I've never been good at taking care of out-of-water plants either, even with instructions ^^; The fish do great though!

[Wobblegong]

that's hard because there are so many things I want to be good at... if I had to pick I guess cooking? I like making food for people but it's never as good as I want it to be.

would also be nice to do some sort of nonprofit work

[Corrupted Unicorn]

I want to be an expert at animation! I want to know all about drawing things and making them move, and to get as good at it as the legends!! 

[Memory]

On further consideration, I think I'd be afraid of choosing anything to "suddenly be an expert at".
Who we are, our hobbies and experiences, kind of make who we are. If I suddenly changed into an expert at something I don't know the first thing about today, I wouldn't be myself anymore. It'd be like missing memories.

Part of the "fun" of being an expert is also not just the skill, but also the memories you make, the people you meet, the events you attend and the little achievements you build up.

[Memory]

I'd like to be an instant expert at being a musician.

[krish]

I think that I'd like to become an expert in architecture. I can only dream of the amount of depth I'd be able to add in my art thanks to the detailed backgrounds I could draw.