If you're talking about physical injury:
* Disabled
* Injured
* Crippled (can be considered offensive, use with caution)
If you're talking about something unoriginal or boring:
* Uninspired
* Uninteresting
* Dull
* Tedious
* Mediocre
* Weak
* Clichéd
* Unremarkable
* Lackluster
If you're talking about something unsuccessful or ineffective:
* Futile
* Pointless
* Ineffective
* Unsuccessful
If you're using it in a more informal, slang sense:
* Bad
* Awful
* Terrible
* Uncool
* Unhip
* Lame-brained
It's important to consider the context and your audience when choosing a synonym for "lame." Some words are more formal than others, and some can be offensive or hurtful.