Calling Current Category?

this might work:

$cat_id = get_query_var('cat');
query_posts('posts_per_page=-1&cat='.$cat_id);
if (have_posts()) :
echo '<ul>';
while (have_posts()) : the_post();
if( get_the_tag_list() ){
echo $posttags = get_the_tag_list('<li>','</li><li>','</li>');
}
endwhile;
echo '</ul>';
endif; wp_reset_query(); ?>

however, you might get a lot of duplicate tags.

query parameters:
http://codex.wordpress.org/Class_Reference/WP_Query#Parameters

the whole code got a bit longer, therefore a pastebin:

http://pastebin.com/qfZQVGcS

to avoid duplicates, the output of the tags is turned into an array, each tag array per post is added into a big array, then filtered into unique elements, sorted, and turned back into an output string in li form.

http://www.php.net/manual/en/function.sort.php
http://php.net/manual/en/function.array-merge.php
http://php.net/manual/en/function.array-unique.php
http://php.net/manual/en/function.explode.php
http://www.php.net/manual/en/function.implode.php

the code outputs the tags of all posts if not used within a category archive; to avoid this, you need to wrap the whole code into:

<?php if( is_category() ) : ?>
THE CODE HERE
<?php endif; ?>

http://pastebin.com/zi2EN4NH

i swapped get_the_tag_list() with get_the_tags() and rebuilt the links; http://codex.wordpress.org/Function_Reference/get_the_tags

hope this works 😉