The heaviest knife I've carried is probably the ZT 0301 (8 oz). For that knife, I carry it in my back pocket. It's just a bit too wide to comfortably fit in my front pocket without really obstructing access to keys, wallet, etc.
For me, weight is less of a factor than the physical size the knife takes up in pocket. For example, the ZT 0200 is actually a bit lighter than the 0301, but it is also bulkier to the point that I haven't yet worked out a comfortable way for me to carry that particular knife. And on the flip side, the Manix2 LW is a bit lighter than the Caly3 CF, but the latter is significantly more comfortable to carry for me.