it is possible to capture the giant corpse flower, provided that you are strong enough and meet the lvl requirement. It will look like a giant tender cirrus when you capture it, rather than the shape you see it when you are fighting it. I actually saw one walking about in Aries, though I am not sure if it is any good.

Another boss you can capture is the Big Tiger in KaMa Cave.

One way to capture lots of bosses:
1.find a quester, and a catcher
2.catcher joins team with quester, who would start the fight
3.quester runs away, either log off or just escape
4.this would leave the catcher(s) alone with the monsters
5.Since quester never finished the quest(he ran away), he can always restart the fight with the catcher, who would keep catching them!!!

WARNING: if you catch and sell too many of these bosses, their price in the market will collapse, much like the Wall Street Crash