I don't reply too much here, usually I just vote but hell what a poll.
Arsenic: easily my 2nd favourite card. Sooo good. Takes a while understanding to assess how good it is, and bc of that it is overlooked among newbs ("a weapon that deals 3 dmg? wtf").
The only problem with it that it rarely takes any skill to make the correct decisions: just play it asap.
PU: top10 favourite as well. A bit limited in use but very effective when used correctly. Just put it into your deck and hilarity ensures.
RT: My fav card. Does soo much. Takes a lot of practice to use properly and thus rewards skilled play.
BTW If anybody is wondering about my top10 fav cards, the list goes (I think):
1. RT
2. Arsenic
3. Fenix
4. Toadfish
5. Lava Golem
6. BW
7. Arctic Squid
8. Deflag
9. PU
10. Lightning
runner-up: nova