I like the idea of the nickname [name]Mack[/name], but would want the proper name to have more substance.
Any ideas? [name]Even[/name] open to far fetched ones 
Somebody once posted a thread about the name Macsen, which was pretty cool.
What about:
[name]Mackenzie[/name] (I know so many find it overly feminine now, but honestly, I’ve come across about 6 boy Mackenzies, and only one girl [name]Mackenzie[/name], so it really doesn’t seem that awful to me)
[name]McKinley[/name] (seems to be the most masculine of the Mc- names to me, personally… Sort of seems semi-patriotic, thanks to President [name]McKinley[/name], too…)
Any [name]Max[/name] name ([name]Maxwell[/name], [name]Maximilian[/name], [name]Maxon[/name]/Macsen, [name]Maxfield[/name], [name]Maddox[/name], etc.)
Good luck!
I also vote for Macsen! I love it, I think it’s a very handsome name (It’s on my list!). Here are some other names I think could work.
[name]Maksim[/name]
[name]Marcus[/name]
[name]Mark[/name]
[name]Cormac[/name]
[name]Maxwell[/name]
[name]Do[/name] you have any McNames on your family tree?
[name]Maddox[/name]
[name]Maxwell[/name]
[name]Marcus[/name]
[name]Matthew[/name]
[name]Mattias[/name]
[name]Cormac[/name]
[name]Magnus[/name]
[name]Maguire[/name]
[name]Macallister[/name]
[name]Macon[/name]
I think [name]Mack[/name] or [name]Mac[/name] is a great nickname for [name]Malcolm[/name] - a cool, solid name.
I agree [name]Emily[/name] - obvious choice is [name]Malcolm[/name]!
I also love [name]Mac[/name] as short for [name]Malcolm[/name] (such a great, underused name!). [name]Cormac[/name] and [name]Macauley[/name] are great choices as well.
Ooh yes [name]Malcolm[/name] nn [name]Mack[/name] is great.
[name]Cormac[/name] and [name]Magnus[/name] too.
There’s the Hawaiian Makaio (it’s the Hawaiian [name]Matthew[/name], prn “Mah-[name]KAY[/name]-o”)
[name]Malachi[/name] is beautiful.
McCormick
Makellan or perhaps Maclellan (one of my good friends has the latter as a last name and I have always loved it)
I don’t think anyone has posted [name]Maverick[/name] yet.
[name]Maverick[/name] is a possiblity.
Ditto what others have said: all the [name]IRL[/name] [name]Mac[/name]/[name]Mack[/name]'s I know are Malcolms.
I have to agree with the others. [name]Malcolm[/name] nicknamed [name]Mac[/name] is the best choice.
I’ve never heard of [name]Mac[/name]/k as a nn for [name]Malcolm[/name], but it seems to work well. I know three guys [name]IRL[/name] who go by [name]Mac[/name], two have surnames beginning with Mc/[name]Mac[/name] and the third is a [name]Michael[/name].
[name]Maxwell[/name]
[name]Maximus[/name]
[name]Mackenzie[/name]
[name]Marcus[/name]
Maxmillion
[name]Cormac[/name] is one of my favourites too. Great name.
I always loved the character of [name]Mac[/name] in the [name]Louisa[/name] [name]May[/name] [name]Alcott[/name] stories, Eight Cousins and A [name]Rose[/name] in Bloom. His fn and mn were [name]Alexander[/name] [name]Mackenzie[/name], I believe. [name]Cormac[/name] is a natural fn for [name]Mac[/name] as well, I think.