Is it possible for Wireshark to drop packets purposely?

I would like to test something like VoIP. I would like to test with some "artificial packet loss". Is Wireshark able to do this? Or is there any good solutions?

You can use tools like WANEM to simulate packet loss. It's a Live-CD, so you can put it on a system between your server & clients.

WANEM as mentioned is a good tool. If you're doing on Linux you can also play with the buffer queues etc, check out this page which has many answer to this questions already including netem and queue examples;

Also, you can use tools like iperf/jperf to saturate a link.

You can also use iptables to drop packets, like this.