MSR, Marmot, OR, BD, Sierra Designs and Julbo, to name a few.  I've sent some pretty mangled glacier glasses back to Julbo a few times and they have always sent me a brand new pair.  Smith has hooked me up a few times but not always.  I still really like Smith sunglasses though.  I also really like Kershaw knifes.  They have replaced a ton of folding knives that have gotten the tip broken off or other minor damage.  They make a great product too.  It never hurts to send a nice schmoozy letter telling them how great they are before hitting them up with any warranty request.