Hi,
on db2 v9.5 on Linux I have one user that only needs access to "list application" command. What is minimum rights I must give to this user? I don't want to give him any other rights except this one.
Regards

He just need to have CONNECT Privilege to the Database inside the Instance. He needs to ATTACH to the particular instance and then submit the LIST APPLICATION command.

according the doc
Authorization
One of the following:
* sysadm
* sysctrl
* sysmaint
* sysmon

my mistake. You are correct. the above authorization is more than sufficient for this. You don't even need to have DB CONNECT authority.