in version 0.5.2 some commands (like +weapon1 etc.) don't work with mouswheel anymore. Use version 0.5.1 instead. If you don't want to pass on 0.5.2 you can do some changes to the source and then compile it(that's what i did, but i only changed it back to the way it was in 0.5.1, but there is some deeper problem to it, so it's only a workaround). If you want to do this, get the 0.5.2 source, open teeworlds-0.5.2-src/src/game/client/components/controlls.cpp with the editor of your choice. Then do the follwing change:
In line 38 remove:
*set->variable = console_arg_int(result, 0) ? *set->variable = set->value : 0;
and add
if (console_arg_int(result, 0))
*set->variable = set->value;
instead of that.
After doing this compile tw and mouswheel will work with those commands.
But as I said this is only a work around, and the devs know about the problem, so I hope it will be fixed in the next release .