I Still think grabbing them by the tail and whacking them against a corner is still the best. When people get CO2 poisoning it is slow and they get really bad headaches before. quick whack done right will be the most humaine and easy thing to do
And if you don't whack just right you have a suffering animal..This is especially true if you're inexperienced.
1.0 Western Slender Glass Lizard; Logos
0.1 Charcoal Cornsnake; Morana
1.0 Golden Gecko; Smoothie
1.1 African Plated Lizard; Cypher and Nara