well there's always Rammstein of course

no but thanks, I'll check these out sometime

and it doesn't have to be avant garde or something related...

Check out Das Ich!

Wumpscut - "Böses junges Fleisch"

Einstuerzende Neubauten is good stuff Judging by what I have heard - perpetumm mobile
what else should I get by them?

The short answer is: everything.

The long answer is:
In my considered opinion, the highlights of their career are:

Drawings of Patient's OT - Their second album, it's got the metal crashings and clangings of their debut, but has an atmosphere just oozing with darkness and uncertainty. The title track is one of their best ever tracks too.

Funf auf der oben Offenen Richterskala The beginnings of EN's more structured era, again, generally a very dark sounding album, plus, it's got a cool Anthony Newley cover, "Sand"

Tabula Rasa - They were often accused of selling out by this point, but that's a pretty stupid accusation. They had the occasional English lyric on this, and a ballad which had some small rotation on MTV. It's probably their most pop album, but none the worse for that.

If you want a kind of best of, get the double live album 9-15-2000 Brussels, superb performances, superb sound quality, superb album.

Um. Get everything.

yep.

I'd really only suggest their first 5 albums:

Kollaps
Zeichnungen Des Patienten O. T.
Halber Mensch
Fuenf Auf Der Nach Oben Offenen Richterskala
Haus Der Lüge

Get any one of those releases and you will not be dissapointed.

their "strategies against architecture" compilations are a good place to start.

''Halber Mensch''
''Tabula Rasa''
''Haus der Lüge''
''Zeichnungen des patienten O.T.''
Or better yet, just "...Get everything."

Great suggestion