Wow. I've never used any of those. Some of them I've never heard of.
Let me explain:
-Vala is a Gnome project, its aims to bring proper object orientation to GObject. Its syntax should be similar like C# and Java.
The Vala compiler translates its code to C.
-Scheme is the second big lisp dialect.
-Erlang is a (interpreted?) script language used by telecomunication systems.
-Eiffel is try to make a sane OO language.
-Object Pascal... ...is the object orientated, more powerful implementation of Pascal by Delphi and FPC, maybe also by GNU Pascal (not too sure).
-Modula 3 and Oberon are successors of Pascal. They are strong typing languages, syntax is similar to Pascal.
Referring to C:
C might be a good tool for realtime/hardware programming, but while pointers and other strange but efficient methods are good for those things, they suck because of their complexity and unreadability for rapid developement, game scripting and every day's programming.
C++ is imo a bloated oo version of C, but it still doesn't have the improvements from C99. It may take years, until the compilers implement the coming, improved C++ standard.
So it is up to your decision and i don't want to bother you with this neither stop you from programming this, but i think, there are reasons someone shouldn't use C for all tasks.
EDIT: All in all, i guess it would be cool for programmers of the above named languages to find out, that their knowledge has another use. That's the reason for suggesting them.
best regards,
Sauer2
EDIT2:
http://seed7.sourceforge.net/faq.htm