I love the name [name]Sam[/name] and have toyed around with it on and off my list for a while. I can’t quite seem to attach myself to [name]Samuel[/name], and [name]Sampson[/name] and [name]Samson[/name] don’t quite fit either. Are there any other options that [name]Sam[/name] could be a nickname for I’m missing?
Why not just [name]Sam[/name]?
I know a boy named [name]Sam[/name] ([name]Samuel[/name]). His mother actually dislikes the full name [name]Samuel[/name], but fell in love with [name]Sam[/name]. Her family encouraged her to use the long form, even though she only ever planned on calling him [name]Sam[/name], the even now, the boy only ever goes by [name]Sam[/name].
I understand wanting a longer form of the name to have something more formal to fall back on though (I have the exact same issue with the name [name]Maggie[/name]…I [name]LOVE[/name] [name]Maggie[/name] but am not fond of any of the long forms).
I like [name]Samson[/name] best of [name]Sam[/name]‘s long forms. The only other “[name]Sam[/name]” name I can think of is [name]Samar[/name], which NB has in their unisex names category. They also have a [name]Samal[/name] in their boys’ list, which I had never heard of before I looked.
Samwise (LOTR, I know)
[name]Samir[/name] (very common Arabic name, meaning ‘friend’)
Bassam (“smiling” in Arabic)
[name]Isam[/name] (“protection, security”)
[name]Sami[/name] (“high, exalted”)
[name]Salomon[/name] (Spanish for [name]Solomon[/name])
Samad (“eternal”)
[name]Samu[/name] (Hungarian version of [name]Samuel[/name])
Sambell, Samber, Sambrook, and Samford could be options.
http://nookofnames.com/2012/02/18/surnames-as-first-names-english-surnames-s-part-1/
The only ones I can think of are Samad and [name]Samir[/name] (I [name]LOVE[/name] this name!), which pps have already suggested. But I wanted to share my experience with this exact dilemma. Before my son was born, I LOVED [name]Sam[/name] but didn’t like any of the long versions (and I liked [name]Samuel[/name] the least). We eventually moved on to decide on a totally different name before he was born and were completely sure that would be his name, then when he was born [name]Samuel[/name] was the only name that seemed right for him and suddenly I loved it. We call him [name]Sam[/name] mostly (sometimes [name]Sammy[/name], sometimes [name]Samson[/name] (for fun), sometimes [name]Samuel[/name]), but I still love his full name. Funny how that works sometimes.
Also, although I can’t think of any, I’m sure there are other names that could get you [name]Sam[/name] as a nn – anything that has those letters in it, pretty much, or that sound. Or maybe ends in [name]Sam[/name]? Nicknames are so subjective. Almost anything can be a nickname if it feels right for you. 
Thanks for all the suggestions! I do really like the name [name]Samir[/name] but have some unfortunate associations with a person so that is sadly out. I think I like Samford and Sambell best. And I can’t believe I forgot Samwise, haha.
@catheyc - thanks for sharing the story of your son, it certainly is funny how that works sometimes.
Samwell is a character from ‘A Song of Ice and [name]Fire[/name]’. He usually goes by [name]Sam[/name].
I went to college with a [name]Samir[/name] my freshman year. I didn’t really know him, but he seemed like a nice guy. He was Egyptian, though, and it seems like one of those names that you couldn’t really pull off if you weren’t Egyptian. I really don’t know the Game of Thrones/A Song of Ice and [name]Fire[/name] series, but I do think Samwell nn [name]Sam[/name] is cool. It sort of reminds me of a masculine take on [name]Samuella[/name] (sam-WELL-ah), without the [name]Samuel[/name] spelling.
The only other way to get [name]Sam[/name] that I’ve thought of is by initials. I had liked [name]Seth[/name] [name]August[/name] [name]Morgan[/name], nn [name]Sam[/name], a while ago. I just don’t think I could commit to the initials nn idea…
Dossam is a character from a book series I’ve been reading, and he goes by [name_u]Sam[/name_u]. I liked it 
[name_m]Samuel[/name_m] gets my vote.
I went to college with an Egyptian named Samih (I think, anyway! I’m pretty sure), and I always thought that was interesting. It sounded a lot like [name_u]Sammy[/name_u]. Before I fell for [name_m]Samuel[/name_m], I had toyed around with the idea of using the initials [name_u]SAM[/name_u], since I liked [name_u]Sam[/name_u] a lot, but not [name_m]Samuel[/name_m] so much. I had thought about [name_u]Seth[/name_u] [name_u]August[/name_u] [name_u]Morgan[/name_u]. I think you could probably do something like S__ Am____, too. Like [name_m]Soren[/name_m] [name_m]Amos[/name_m]? [name_m]Sebastian[/name_m] [name_m]Amir[/name_m]? etc.
Good luck!