My thoughts.
TNT: Not sure I understand how it should work but sounds interesting.
Nuke: I like it. If you were planning on using timebomb, that doesnt work so well. Youd prolly need to code it so forceplayersuicide within a radius. Then immunity to those using IN_DUCK. OR You could also do is a timer on the person who got the present and does a fakeclientcommand "explode" on that person and also any enemies within radius. Youd end up with alot of visual exploding parts lol. I dont think that would lag...
Blue Shell: You could hit them with a bolt of lighting that reduces their health by 50%, or 75%. I think theres a sprite/particle that does that lighting effect? Or is that CSS only? : /
Next Gen: Bloom = bad.
Any big graphics related effects = bad.
1-up: Thats a kewl idea. Id change it to, if you die somewhere, within 10 seconds you will respawn back at the same spot. However, you may have serious conflicts with peoples respawn plugins with this...