This has probably been addressed by others in similar manner, so forgive my ignorance if that’s the case. In any event, here’s my house rule suitable for use in any D&D Gamma World game (and a few straight D&D ones as well):
“Whenever a character invokes a power or object whose use is limited to once per encounter, they must describe how incredibly cool that effect makes their character look and how awesome a power it is. Failure to do so will result in a -2 penalty to the attack/resolution roll. Thus, don’t tell me “I use fiery flare on this guy,” and point at the counter. Tell me, ‘I roll up my sleeves and ignite my hands. Staring down at the cringing badder, I say “How about a little fire, fuzzy britches?” before hurling a skull-shaped ball of napalm at him.’ Doing so negates the -2 penalty and may even earn you a small bonus.
“This rule may also affect the use of skills at the game master’s discretion (And probably should).”