There are precisely three amusing things in/about Shaun of the Dead.
1) These lines:
Shaun: David, kill the Queen!
Shaun: The jukebox!
2) The fact that they never explain what caused it.
3) Sorting through the record collection for albums suitable for tossing at "the assailants".
Runners up because I like lists of fifteen:
4) The front door running gag.
5) The random jukebox's song choice.
6) These lines:
Shaun: [about Ed] He's not my boyfriend!
Ed: [handing beer to Shaun] It might be a bit warm, the cooler's off.
Shaun: Thanks, babe.
7) The channel-changing to complete the sentence.
8) The "assailant" moaning in time to White Lines.
That is it. I cannot even come up with ten.