I was doing a regular yum update this morning and noticed that my fedora system has a significant number of GUI programs installed...I've never used most of them yet.
So,i was wondering if someone else is getting their work done with such utilities.It is too difficult and time consuming for me,to try all of them one by one.

Please list which programs do you use most frequesntly on your linux system...so that i can get benefitted too.

In approximate order of how often I use them (1=most often), here are the ones I can think of off the top of my head:

1- Firefox. I would use Chromium, but I've got so many Firefox extensions for which there are no Chromium equivalents.
2- Pidgin. Mostly as an Identica client, running in the background.
3- gedit. It's surprising how often a simple text editor is useful.
4- GIMP. A very powerul image editor.
5- Clementine. A music player/manager inspired by Amarok 1.4.
6- Unison. For making backups of my very large music collection.
7- TrueCrypt. For encrypting files.

Firefox.
Deluge.
vlc.
Terminal.

Iceweasel (firefox lol)
Banshee
VLC
Gedit
Libreoffice Writer
Empathy (I used to prefer pidgin but sometimes it just wont work)
Skype
Evince
Synaptic

I have a huge amount of GUI apps installed and I have used each one but the list above is my daily usage in Gnome and most get used in Enlightenment, Fluxbox, XFCE, LXDE, MATE (Mate has gnome apps with different names). I don't use KDE often so I don't know what I would use in that.

Firefox
Claws Mail
zsh
vim
Virtualbox
MPlayer
Audacious
Thunar
Bunch of command line programs, like htop, ssh, rsync, ...

GUIs:
Firefox
Kwrite
VirtualBox
Dolphin
VLC
not necessarily in that order.
CLI stuff in Konsole, or the terminal.

gnome-terminal - filesystem
gpodder - podcasts
realcrypt/truecrypt - sharing encrypted volumes with Windows
VMWare Workstation - virtualization
calibre - ebooks conversion for Amazon Kindle
handbrake/vobcopy - DVD ripping
netbeans - Java coding
eclipse IDE - Java & python coding
Visual CertExam Suite Pro (Wine) - Prometric Certification Testing
keepass - encrypted passwords management
firefox - web

Gedit
Abiword
K3b
FireFox
Opera
Totem
VLC
Thunar/Dolphin
Kget/Gwget
Screen Shot
Xchm
Qps
Mdic
F-Spot
Konqueror
Evince
SoundConverter
KMag

On Fedora/CentOS/Scientific Disk-Utility ,Main-Menu ,Alacarte

Firefox
Thunderbird
Gnome-commander
OO.o Calc and Writer
VMWare Player
VLC
Wine (well a few items installed under Wine)
gedit
TrueCrypt
K3b
Beyond Compare
recoll
utilities such as System Monitor, Baobab, Synaptic, Update Manager

Firefox
Abiword
Musique

I think the OP is interested in the little tools rather than the full applications? In that case, my common ones are evince, eye-of-gnome, gcalctool, brasero, file-roller, system-monitor, user-mount. If it's applications, then the usual one for me are opera, claws-mail, openoffice, gnucash, and wine.

firefox
pidgin
gnumeric
abiword
gramps
lxterminal
geany
gftp
mirage
gimp
yumex
pcmanfm
evince
scrot
conky
gnomebaker

If we talk about interesting command line aplications, then

metapixel (great one to make photomosaics)
testdisk/photorec (restore erased partitions and files)
libcaca and associates (cacademo/cacafire/cacaplay/cacaserver/cacaview/toilet) ascii art/videos, banners ...
wget (http swiss knife)
nmap port scanning
aircrack-ng (airodump-ng, etc...) Wireless cracking
ssh (secure shell)
asterisk (PBX)
rsync (easy Backups)
strings (scan for strings in executable files)
sensors (informs about the status of your pc sensors)
wol (wake on lan)
dosbox (for the oldies goldies)
gpg (encryption tool)
gdb (disassembler)
hexdump (self explainable)
file (inform of the file tipe -magic number identification-)
john (john the ripper -password cracking-)
lame (audio convert)
screen (allows to unlink a session from a terminal so that you can access that session from different terminals)
steghide/stegbreak/stegcompare/stegdetect (steganography tools)
stereograph (tool to create 3d images that you can see without glasses, just adjusting your eyes)
shred (erase a drive making it almost imposible to recover).
tor (the onion router, anonimity network)
fortune (fortune cookies)

Wow, there is plenty of GREAT material up there, don't take it lightly.

By the way, in my previous post I forgot about blender, a great open source app for 3D creations.

Opera
LibreOffice
Konqueror
Kate
Pan
Nautilus
VLC
XAMPP

- Google Chrome
- Thunderbird
- Pidgin
- Skype
- irssi (terminal-based IRC chat client)
- Filezilla
- Bluefish
- Kompozer
- Rhythmbox
- VLC