I'm coming up to 24 weeks with DS2. Need to agree on a name at some point.
DS1 was easy, we agreed on his name on the day of the scan and it just stuck. This time it's really hard! DH has totally different taste to my ex as well and I can't predict what he will like at all.
I should admit, I'm probably the pickier of the two of us. The problem is that it seems with boy's names I either really like them (1%), I really hate them (80%), or I find them okay but totally and utterly bland (the rest). I've also taught children which seems to add another layer of nightmare to the whole process 
Criteria (Skip to summary for less waffle)
We're English but live in Germany. It has to work in English and German. It can be a German name or an English name. According to German rules: It can't be a made up name. If it's not recognisable as either English/German by the average German person because it's unusual, we may be asked to get a letter from the consulate confirming it's a real name. It's also not allowed to choose a name which is more commonly known as a surname - something like Thomas would be fine, something like Bailey is not (real example a friend was refused). I don't mind if it's common or unusual currently but defo not a name you'd associate with somebody of a certain age group, like Wolfgang, or Steve.
Common German letter/pronunciation problems:
J is pronounced like Y
TH is pronounced like T or S
W is pronounced like V
V can sometimes come out like W
R as a beginning letter can be tricky.
Just generalisations, but does rule out a few names we like, particularly J names. Worth noting if they are very common English names, like James, they are pronounced fine, but names with a German equivalent like Jacob/Jakob (Yak-ob) won't generally come out as we'd hoped!
We will use one of two middle names which both end in the sound -ew. Our surname is one syllable with the -e- sound, and it sounds like a real word, so names which are also real words often sound ridiculous. Think along the lines of Webb (but it's not Webb). Grey Webb = definite no. Based on how these sound with the middle and surnames I've ruled out names ending in oo/ew, o, m, p, v or ch. DH prefers two syllables or at least a two syllable short form (e.g. Freddy).
We would really love a connection to space, fantasy or nature, but this isn't required (it just gives it more chance of breaking through the "meh" or "oh god no" filters). Apart from Welsh and German connections we don't have any other geographical links. I'm not really keen on names which mean things like "warrior" or other things relating to violence/dominance - I'm aware this sounds totally and utterly bonkers but I don't like the association of male = violence. And we're not religious and DH is quite keen to avoid religious names - but IMO this only really rules out things like Gabriel, Noah - something which is extremely common but also happens to be a biblical name like Matthew might be OK. The meaning probably isn't a dealbreaker - just a nice to have.
So far we've gone through:
Lars - DH doesn't like because "he will name the baby lala" - I still like, and think this is a stupid reason.
Robin - like the connection to nature/woodland, two syllables, Robin Williams, general sound. But I was unsure as it is quite close to DS1's name. DH has now gone off as he's realised it can be used for a girl too.
Leo - we may come back to this because it's the one we've both stuck on for the longest, but we were both under the impression that the other wanted a longer "proper" form and couldn't agree on one. I'm not hugely sure about the -o ending with either -ew middle name. DH suggested Leon which I really don't like. And I don't think Leon can be shortened to Leo. Now he's gone off it - not sure if this will come back.
I like but DH doesn't: Max, Emil, Tobias (Toby), Elfrid (but agree this is a bit too out there), Leonidas (Leo)
Currently (tentatively) considering - Idris. I love this name, have always loved it (my Grandma was Welsh and we spent a lot of time in Wales during my childhood) plus it reminds me of dragons. I like that Idris is a legend too, and an astronomer! DH is a bit unsure because he hadn't heard of it before, but I think he might be warming to it? He liked Idris Elba in some film or another. I do think the Germans will tend to pronounce it ee-dris with a rolled R but I don't mind that.
Summary:
Boy's name
Works in English and German
Two syllables (or two syllable short form)
Not ending in oo/ew, m, p, v, or ch
Not a real word
Not a made up name
Not a surname
Bonus for connection with space, fantasy or nature
Preferably not meaning something violent or religious
If you can come up with anything either one of us likes I will be very impressed