I only follow a few, but the ones I love are:
Roger Ebert - great posts about movies, politics, and life.
Mischa Collins - just a hilarious guy in general.
Jim Beaver - a former Doper(briefly) and a very interesting man. I keep meaning to read his recent book on his life.
You?
Chrissy Teigen is more than just a pretty face.
Anyone from MSNBC
My most favorite people to look after over there is my most favorite singers James Otto and LeAnn Rimes . 
God bless you and them always!!!
Holly (a day one fan of LeAnn)
Nathan Fillion. Will (and Anne) Wheaton. Bruce Campbell. Darth Vader (satire, of course). Maura Isles/Jane Rizzoli when the show is running. David Hewlett occasionally posts his kid’s adventures. Alton Brown. Adrianne Curry if you like a little bit of crazy. Mary Lynn Rajskub. Felicia Day. Rainn Wilson. There are quite a few actors who do live tweet chats when their TV shows are aired - Walking Dead and Being Human are examples.
I enjoy Adam Baldwin, but his political views may not be your cup of tea.
I check in every few days to see what people are up to, and hopefully get a laugh or three. It also looks like I like snark quite a bit.
What is a “day one fan”?
In any even, I don’t have a twitter, but if I did, I’d want to follow Will Farrell.
^^^ I’ve been a fan of her ever since her first song on the radio.
God bless you and her always!!!
Holly (a day one fan of LeAnn)
Another person that I think leaves good messages is the guy that plays Danny Regan on the Blue Bloods show.
God bless you and him always!!!
Holly
The Iron Sheik’s feed is absolutely hilarious, especially if you were in any way a fan of wrestling in the '80s.
Stephen Fry
Seconding Wheaton
Again, depending on your politics, Michael Moore, who just today reports through his Twitter that Emad Burnat (and his wife and son), Palestinian farmer turned filmmaker, director of “5 Broken Cameras”, the 1st Palestinian doc ever nominated for the Oscar, was detained at LAX for an hour and a half last night when he arrived in the US to attend the Oscar ceremony.
I get several results for Will Wheaton. Which is the real deal?
Which “Walking Dead” actors live tweet during the show?
@wilw is (the real) Wil Wheaton’s Twitter handle.
It’s Wil Wheaton, but when looking for a public figure’s Twitter account, when in doubt look in their profiles for the one with a blue icon containing a white checkmark. This means they’ve been verified by Twitter to be who they claim to be.
Yup! I was going to come in and mention this one - @the_ironsheik get you in old country way! Warning on this one - definitely NSFW. It is crude and rude and lots of F-bombs. If you don’t get or remember The Iron Sheik’s wrestling schtick during the 80’s this one will leave you with a big WTF?!?
Others I enjoy…
@fakedansavage - the real Dan Savage, sex advice fun.
@TheTweekOfGod - C’mon, God is a celebrity right?
@Jesus_M_Chris - See above.
@SarahKSilverman - Sarah Silverman, doesn’t seem to tweet alot but has some good gems when she does.
@scalzi - John Scalzi, sci-fi author and lots of funny tweets.
@sarcasticrover - NASA’s sarcastic twitter feed from their Curiosity rover on Mars. Poor little guy, abandoned on Mars for science!
@pattonoswalt - Patton Oswalt, easily my favorite on twitter.
So there you go!
Oh, and @ActuallyNPH… which is actually Neil Patrick Harris. 
The only person I follow on Twitter is Ke$ha.
Not a celebrity, but @TheOnion tweets regularly brighten my day.
Most of mine have been mentioned: Fillion, NPH, Wheaton. I also follow Jewel Staite and Patton Oswalt. Patton can be very funny when he gets on a roll.
Anna Kendrick is very funny on Twitter.
Yeah Wil Wheaton is good and seconded The Onion.
I also enjoy Bill Maher and Denis Leary.
MtM