Harrison- I'm not a fan of. Feels like a last name to me. And these ubber popular 'son' names don't make sense to me unless he'd actually be the 'son of... (in this case, Harry).
Reid- I think this would make a solid MN, but not such a fan for a FN. Personally I'd only use this name if the kid was a red-head. I prefer the spelling Reed.
Theodore- A very awesome name. Great meaning. Classic. Lots of history. But not overly common these days. Great name.
Pierce/Piers- I'm not such a fan personally, but it's not a bad name, just NMS. It feels a little pointed.
Dillan- I'd spell it Dillon. I like this name quite a bit, for me it's just too high up the popularity charts (spelled as Dylan) (#33), but I'm picky that way.
Ethan- Also a name that I quite like, but it's just way too overused for my taste (#7 most popular in 2011, and from 2004-2010 was always in the top 5 most commonly used).
From your list, I'd definitely go with Theodore
I also forgot about Anders.
Harrison- I actually like this name a lot, it is a strong, masculine name that is easy to say and spell.
Reid-I like this name too.
Theodore- I know this name is getting quite popular lately, but I always think of Theodore the chipmunk from Alvin and the Chipmunks, can't help it.
Pierce or Piers- They are nice, but not my favorite,
Dillan- This is a nice name.
Ethan-I very much like the name Ethan, but happen to know quite a few Ethan's.