Beep beep! Gun nut here!
While I absolutely love FN Herstal's weapons, including the FiveseveN, it would be a poor choice for zombies, dude. It uses a special kind on ammunition, the same as the P90, and it has a high muzzle velocity, and it jacketed to promote armor penetration.
Freakin sweet gun, though. Accurate as hell.
As for me, there are tons of guns I'd love to have, including;
M82/M107 (yes, they're legal)
Tactical .45 (I'm sure most of you know the 'Tac. 45' from Black Ops II...)
MRAD/M98B
MSR
S&W M&P 15
LaRue Tactical M4
AK-74M
M91/30 PU (I want mine back, dammit!)
1911 Tactical Pro Carry (Famous for; "I JUST SHOT MYSELF!" Awesome gun though. I want one in an olive matte finish. ^^)
M200 LRSS (Now there's no reason at all for me to have one of these unless I live in, say, Kansas, or Alaska, in the middle of goddamn NOWHERE, but I'd freaking LOVE to have one...)
And, finally.
The Gepard GM6 Lynx. Imma link a video. It's that awesome.
That's a .50 BMG! Turns the recoil into nothing!